Skyrim:Shalidor's Insights

Quick Walkthrough
# Talk to Urag gro-Shub.
# Travel to the indicated location and retrieve Shalidor's Insights.
# Return to Urag gro-Shub.

Detailed Walkthrough
Talk to Urag gro-Shub and ask him if there are any special books he's looking for. He will tell you that he's looking for a book Arch-Mage Shalidor wrote so he can translate his writings. The book can be located in the boss-level chest of any dungeon in the game including ones added in Dawnguard and Dragonborn, meaning that your destination is randomly selected from over 140 possible dungeons.  For specific details about the target location, see its place page; details about any possible conflicts with other quests are also provided there.

The book is in the dungeon's boss chest, normally located at the end of the dungeon. Return to Urag gro-Shub and return the book. He will say that it will take about a day to translate the writings.

The quest will complete at this point and clear from your journal, although you will have written that you still need to return to Urag after the book has been translated. 

Wait for at least 24 hours, and when you return Urag will tell you he's finished translating the text. He will give you three identical copies of one of several possible "Shalidor's Insights" scrolls, or will pass on any knowledge gained from the writings in the form of a one-point skill increase to any magic skill other than Enchanting.

Notes
Which scrolls or skill boost you earn is decided when you hand over Shalidor's Insights to Urag gro-Shub. It is possible to obtain the reward you prefer by saving before giving him the book and reloading the save until the desired reward is obtained.
If the quest marker points to Druadach Redoubt, it is possible to complete this quest very easily by doing the Forsworn chain in Markarth, as this is where Madanach has his base of operations. All of the Forsworn in this area are friendly if you completed No One Escapes Cidhna Mine, as long as you sided with the Forsworn in the mine.
The quest may point to a number of locations which cannot be accessed without completing certain other actions. You may wish to avoid clashes by reloading the game and getting another location. Following is a list of locations and the actions needed to be undertaken to complete this quest:
Rebel's Cairn: partial completion of Find Red Eagle's Sword / Rebel's Cairn.
Snow Veil Sanctum: complete Speaking With Silence. The quest marker may also point to the back door, but you still must complete Speaking with Silence.
The Katariah: complete Hail Sithis! This location is the most common reason why the quest marker does not appear. (This is addressed by version 1.2 of the Unofficial Skyrim Patch; the Katariah can no longer be chosen as a target location for this quest.)
Ysgramor's Tomb: complete Glory of the Dead.
 

Bugs
 
Vokun's Throne Room may be accessed by utilizing a follower to open the gate blocking the player from the antechamber exit above the first room.  This is accomplished by bringing a follower after clearing out the entire dungeon (clearing out the dungeon may be necessary), climbing up the pile the rubble, in the first room, besides Anska, and using Whirlwind Sprint to access the walkway leading to the exit from the antechamber.  The follower will run through the dungeon and eventually appear on the other side of the gate.  The follower can then be instructed to pull the chain, thereby opening the gate and permitting the player into Vokun's Throne Room.  Unconfirmed on PC.
  This can be made reachable using console commands, either to resurrect Vokun and kill him again (select the body, not his ashes) or to simply pass through one of the closed gates (use 'tcl' to turn clipping on and off).
 
To fix this you can type in console  , look for a line REF 'Book'->"(x), x is id you need, then jump and open console again midair so the book wont fall under ground, type in console   where x is id you got previously, and last type  . Look for a book on ground.
 

Quest Stages