<PAGE>
 
                                   FORM 10-K/A

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

(X) ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT
OF 1934 (FEE REQUIRED)

For fiscal year ended   December 31, 1997
                        -----------------

( ) TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE
ACT OF 1934 (NO FEE REQUIRED)

Commission File No. 0-17750
                                 MERCOM, INC.
--------------------------------------------------------------------------------
            (Exact name of registrant as specified in its charter)

           Delaware                                   38-2728175
--------------------------------                ----------------------
(State or other jurisdiction of                    (I.R.S. Employer
  incorporation or organization)                 Identification No.)


105 Carnegie Center, Princeton, NJ                       08540-6215
----------------------------------                     --------------
(Address of principle executive offices)                 (Zip Code)

Registrant's telephone number including area code:            609-734-3737

Securities registered pursuant to Section 12(b) of the Act:   None

Securities registered pursuant to Section 12(g) of the Act:

                     Common Stock, par value $1.00 per share
                     ---------------------------------------
                                (Title of Class)

Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days.
                               YES  X            NO
                                   ---              ---

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405
of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K (X).

As of February 28, 1998, 4,787,060 shares of Common Stock were outstanding. The
aggregate market value of the shares held by non-affiliates of the registrant
(based upon the average of the bid and asked prices of these shares quoted by
the National Quotation Bureau, Inc. and the OTC Bulletin Board on February 28,
1998, of $9.75 per share) was approximately $17,772,463.

                   Documents Incorporated by Reference - None
                   -----------------------------------
<PAGE>
 
                                   PART III

Item 12. Security Ownership of Certain Beneficial Owners and Management
-------- --------------------------------------------------------------

Security Ownership of Management

         The following table sets forth the beneficial ownership of the
Company's Common Stock, as of April 1, 1998, by each director, the named
executive officers and by all persons, as a group, who are currently directors
and executive officers of the Company. Each director or executive officer has
sole investment and voting power over the shares listed opposite his name except
as set forth in the footnotes hereto:


<TABLE>
<CAPTION>

                                               Number of Shares            Percent
         Name of Beneficial Owner             Beneficially Owned          of Class
         -------------------------           -------------------          --------
<S>                                          <C>                          <C>
John J. Gdovin                                      --                       --      
Bruce C. Godfrey                                    --                       --      
Mark Haverkate                                      --                       --      
Clifford L. Jones                                   300                      *       
Michael J. Mahoney                                  --                       --      
David C. McCourt                                    --(1)                    --      
Raymond B. Ostroski                                 4,000                    *       
Harold J. Rose, Jr                                  --                       --      
George C. Stephenson                                5,000                    *       
Timothy J. Stoklosa                                 --                       --      
All Directors and Current Executive                                                  
Officers as a Group (15 persons)                    9,300                    *       
</TABLE>


----------------------------
*      Less than 1%.

(1)    Excludes 50,000 shares which are owned by Mr. McCourt's wife. Mr. McCourt
       disclaims beneficial ownership with respect to said shares.
<PAGE>
 
Item 12. Security Ownership of Certain Beneficial Owners and Management,
-------- ---------------------------------------------------------------
Continued


Cable Michigan

         Set forth below is certain information regarding the beneficial
ownership of the Common Stock of Cable Michigan as of April 1, 1998, by each
director, the named executive officers and by all persons, as a group, who are
currently directors and executive officers of the Company. Each director or
executive officer has sole investment and voting power over the shares listed
opposite his name except as set forth in the footnotes hereto:

 Directors and Named               Number of Shares           Percent of
 Executive Officers                Beneficially Owned (1)     Outstanding Shares
 ------------------                ----------------------     ------------------

 John J. Gdovin (2)                        1,743                   *
 Bruce C. Godfrey (2)                      4,741                   *
 Mark Haverkate (2)                        4,596                   *
 Clifford L. Jones                            --                   *
 Michael J. Mahoney (2)                    4,878                   *
 David C. McCourt (2)(3)                  12,382                   *
 Raymond B. Ostroski                      18,419                   *
 Harold J. Rose, Jr.                          --                   *
 George C. Stephenson                         --                   *
 Timothy J. Stoklosa                       1,014                   *
 All Directors and Executive
 Officers as a Group (15 persons)         47,773                   *

* Less than 1%.

(1) Includes forfeitable Matching Shares (as defined below), and Share Units (as
defined below).
<PAGE>
 
Item 12. Security Ownership of Certain Beneficial Owners and Management,
-------- ---------------------------------------------------------------

Continued

(2)       Under the Cable Michigan Executive Stock Purchase Plan ("ESPP"),
          participating executive officers who forgo current compensation are
          credited with Cable Michigan "Share Units", the value of which is
          based on the value of a share of Cable Michigan Common Stock. ESPP
          participants who elect to receive Share Units in lieu of current
          compensation are also credited with restricted "Matching Shares,"
          which vest over a period of 3 years from the grant date, subject to
          continued employment. Matching Shares, unless forfeited, have voting
          and dividend rights. (In connection with the Restructuring, Share
          Units and Matching Shares will be adjusted in an equitable manner.)
          The holdings indicated include Share Units and Matching Shares. The
          table below shows, in respect of each named executive officer, the
          number of shares of Cable Michigan Common Stock purchased outright,
          Share Units relating to Cable Michigan Common Stock acquired by each
          named executive officer in lieu of current compensation, and the
          forfeitable Matching Shares of Cable Michigan Common Stock held by
          each named executive officer:

<TABLE>
<CAPTION>

                                           Share Units                                        Total Shares
                                           Acquired Under                                     Purchased and
                               Shares      the ESPP In         Total Shares    Restricted     Acquired and
                              Purchased    Lieu of Current     Purchased        Matching      Restricted
                              Outright     Compensation        And Acquired      Shares       Matching Shares
                              ---------    ---------------     ------------    ----------     --------------- 
 <S>                          <C>          <C>                 <C>             <C>            <C>
 John J. Gdovin                   677             533             1,210             533            1,743
                                                                   
 Bruce C. Godfrey               1,251           1,745             2,996           1,745            4,741
                                                                   
 Mark Haverkate                 2,392           1,102             3,494           1,102            4,596
                                                                   
 David C. McCourt               2,894           4,744             7,638           4,744           12,382
</TABLE>


(3)      Includes 56 shares of Cable Michigan Common Stock which are owned by
         Mr. McCourt's wife. Mr. McCourt disclaims beneficial ownership of such
         shares. Does not include 3,330,121 shares of Cable Michigan Common
         Stock held by LTH. David C. McCourt owns 10% of the Common Stock of
         LTH. The remaining 90% of Common Stock of LTH is owned by Level 3.

Security Ownership of Certain Beneficial Owners
-----------------------------------------------

        So far as is known to the Company, as of April 1, 1998 no persons,
except those listed below, owned beneficially more than five percent (5%) of the
outstanding Common Stock. With respect to the named persons, the following
information is based on Schedules 13D, 13G or Form 4 filed with the Securities
and Exchange Commission ("SEC"), copies of which were supplied to the Company by
said persons. The table below discloses the name and address of such beneficial
owners, the total number of shares beneficially owned by each and their
percentage of ownership in relation to the total shares outstanding and entitled
to vote.
<PAGE>
 
Item 12. Security Ownership of Certain Beneficial Owners and Management,
-------- ---------------------------------------------------------------

Continued


Name and Address of                     Amount and Nature of           Percent
Beneficial Owner                      Beneficial Ownership (1)         of Class
-----------------                    --------------------------       ----------
Cable Michigan, Inc. (2)                     2,964,250                  61.92%
105 Carnegie Center
Princeton, New Jersey 08540

Lappin Capital Management, L.P. (3)           600,951                   12.55%
767 Third Avenue, 16th Floor
New York, New York 10017

--------------------------------

(1)    The number of shares stated in this column includes shares owned directly
       or indirectly, through any contract, arrangement, understanding,
       relationship or which the indicated beneficial owner otherwise has the
       power to vote, or direct the voting of, and/or has investment power.

(2)    Based on information set forth in Cable Michigan's Schedule 13D filed on
       September 30, 1997.

(3)    Based on information obtained from Form 4 for the Common Stock of the
       Company filed through December 3, 1997, with the SEC by Lappin Capital
       Management, L.P. and LBL Group, L.P.


<PAGE>
 
                                   SIGNATURES
                                   ----------

         Pursuant to the requirements of Section 13 or 15(d) of the Securities
Exchange Act of 1934, the Registrant has duly caused this report to be signed on
its behalf by the undersigned, thereunto duly authorized.

                                        MERCOM, INC.


Date:    May 6, 1998                    By   /s/ David C. McCourt
                                          ----------------------------
                                                 David C. McCourt, Chairman
                                                 Chief Executive Officer



         Pursuant to the requirements of the Securities Exchange Act of 1934,
this report has been signed below by the following persons on behalf of the
Registrant and in the capacities and on the dates indicated.


<TABLE>
<CAPTION>

         Signature                    Title                                 Date
         ---------                    -----                                 ----
<S>                                 <C>                                     <C>
 /s/ David C. McCourt               Chairman                                May 6, 1998  
--------------------------          Chief Executive Officer 
    David C. McCourt                      



 /s/ Mark Haverkate                 President                               May 6, 1998  
--------------------------          Chief Operating Officer 
    Mark Haverkate                                        


                                    Executive Vice President,
 /s/ Timothy J. Stoklosa            Chief Financial Officer and             May 6, 1998
--------------------------          Treasurer
    Timothy J. Stoklosa             (Principal Financial Officer)           
</TABLE>