Note that you usually will play the V7 chord at the second beat in
the last bar.  This creates a turnaround.  Listen to how the V7 chord function in
that context: It creates some tension, giving the verse a restless end where
you cannot stop.  The tension is released when you are returning to the I chord,
or the tonic chord as it also is called.  We will look more at this V7-I
relationship later.  But be sure that you can identify the tension created by
the 7th chord and how it is released by returning to the I chord.  The music is
coming home when it arrives at the I chord. 

You will never end a blues song at the V7 chord.  In the last
verse, you have to stay at the I chord.  You might also hear a I7 chord played
at the end. 

Books covering the progression -

Gig Savers - Blues Changes for Serious Players
The blues is one of the most played styles and forms of music.  This booklet presents alternate changes and many chord substitutions for the blues in a way that allows them to be transposed into any key.