Can I ask what this is/does and where it is to be found? Ta!
Its a quest found north of College of Winterhold from a mage hermit, you touch on it while on the MQ.
Its a book given to you by Hermaeus Mora, the daedric prince of knowledge. When you read it, you choose a patch of the warrior or mage or theif, giving you 5 skill points in all the skills of the class. For example, you choose the Warrior path. you get 5 skill points in Smiting, 1 hand, 2 hand, block, heavy armor and archery.
@Op "Note: After Patch 1.2.11.0 this exploit has been broken. Doing this will render bookshelves unusable, however using the bookshelves in The Arcanaeum in the same way as the above exploit will have the same effect. Even after the patch." http://www.uesp.net/wiki/Skyrim:Discerning_the_Transmundane