You cannot use a tome in the Party Camp (for example, if you bought one from Bodahn Feddic) on any character other than the Warden. When you have a character selected that can use the tome, the tome will not be grayed out in your inventory, but the Use button will be grayed out. To fix this, leave the camp and make sure the character you want to give the tome to is in your party. When you are in a different location, you will be able to use the tome.
You can get Bodahn's initial offering twice: immediately upon your initial camp visit and any subsequent visit (until The Landsmeet); see this article for details.
Some pre-order versions of the game offered additional tomes. These are available in your main character's inventory when you start a new game. There were some issues for Dwarf Noble Origin characters losing the tomes; these can be resolved most easily by updating to the most recent version of the game.
You can create leveling issues if you use the duplicate item exploit to create extra talent tomes, since you can end up with more talent points than there are talents. By level 20, all characters will choose at least 21 talents; there are only 40 base talents for rogues, 56 for warriors, and 68 for mages. Use caution as some talents are not available until reaching higher levels.
xbox360 Players report being unable to use either "Physical Technique" or "Arcane Technique", depending on which was most recently acquired. Work around this by using the one that works and then the other. Alternatively, sell to a store and buy back the one you want to use first.
Some players report being unable to use a tome for its intended class. This can be fixed by either saving, reloading, then trying again, or by removing all other tomes out of inventory (temporarily selling the others to a vendor or storing them in the Party Storage Chest).
When using Tomes, if you fill up the talents/skills you will be unable to complete the Level Up, resulting in you being stuck on selecting a Talent/Skill. The fix is to go back to the Attributes and selecting Auto-Level. If trying to reach 99 on a specific stat using the tomes takes a very long time. Although duplicating Mortal Vessel is the best, and quickest, option to further level your attributes once you've maxed out your skill tree, making leveling a stat even up to the far reaches of 99 a ridiculously easy task if it is simply hotkeyed to an action button, with no subsequent menu navigation necessary until cashing it in. (Confirmed on [Xbox})