Skyrim:Black Book: Untold Legends (quest)

Quick Walkthrough
# Read the Black Book Untold Legends in Benkongerike Great Hall.
# Make your way through Apocrypha‎.
# Learn the Black Book's hidden knowledge.
# Choose your reward.

Detailed Walkthrough
 
There are five chapters: Chapter I is basically a corridor that leads to Chapter II it contains no enemies and only three of soul gems in the way of loot.  These can be found at the very end of the chapter, at the final bend just before the book that leads to Chapter II.  

Chapter II has exits to both Chapter III and Chapter IV, enabling you to bypass Chapter III if you wish. There is a leveled lurker to battle before reaching either exit. The lurker is standing near a Font of Stamina and a Font of Magicka. There is another Font of Magicka by the exit to Chapter IV.  The exit to Chapter IV can be found by taking the corridor south and then west; whereas the exit for Chapter III is taking the corridor north.   

Chapter III contains a seeker, a spell tome and a container of loot. These are all in the same enclosed starting area, so that the Seeker will attack you just as you enter the Chapter; the spell tome is in the beginning area as well.  There is no direct path from Chapter III to Chapter IV, so you do have to return to Chapter II.  

Chapter IV contains the most loot including four stealth based skill books, two soul gems and four containers of loot as well as three seekers to battle. It starts off on an open platform with two Fonts of Stamina; walking down the corridor will take you past a well-lit Font of Magicka.  You will head south into another open area; all the Seekers are here together.  There are various landings here going in roughly the eight cardinal directions; the north-east one contains a locked treasure pod, a soul gem, and the four skill books.  East is another locked pod and another Scrye which opens the middle.  Southeast goes nowhere.  South is initially unclimbable.  Southwest contains another locked treasure pod.  By the west gate is a Scrye which opens said gate.  Inside is another Scrye which opens the east landing.  There is a pod to the northwest.  North returns you to the corridor to Chapter II.  The middle Scrye opens out the southern stairs, allowing exit to Chapter V.

Chapter V contains a corridor that initially points towards the final reward, but may bend to the left or right whenever you move down the corridor. If it does, you'll be directed towards a room with a leveled lurker. Kill the lurker and a door will open behind it, allowing you to return to the central room. Once any side areas have been dealt with, the corridor should return to its original position, leading to the Black Book: Untold Legends.

Rewards
Bardic Knowledge — Summons a spectral drum that plays for you, increasing stamina regeneration for you and nearby allies for 300 secs.
Black Market — Summons a Dremora merchant to trade with you for 15 secs.
Secret Servant — Summons a Dremora butler to carry your excess items for 15 secs. (Max carry weight 148)

Achievements
One achievement is related to this quest:
 

Notes
There is a table in Chapter IV that has the four skill books The Gold Ribbon of Merit, Advances in Lockpicking, Beggar, and The Rear Guard, which train archery, lockpicking, pickpocket and light armor, respectively.
You can change the reward at any time by traveling to Solstheim and re-reading the book. This will transport you to Apocrypha near the reward location and you can select a different one.

Bugs
 
  Use the   console command to clip through the door.
 
  Use the   console command to clip through the door(s) and regain your items.
 

Quest Stages