The first installment of Baldur's Gate series feature a series of tomes & manuals which allow the player to permanently increase a character's ability scores by one point. The book is to be placed in quick-slot and is destroyed upon usage. Overall there is one for each score, with the exception of the Tome of Understanding for wisdom, of which three exist.
It is important to note that the attribute raise for companions does not carry over into Baldur's Gate II and only an imported protagonist enjoys the continued augments, if the player were to use the Manual of Gainful Exercise to raise Viconia's strength from 10 to 11 in BG1, she will still have her default 10 strength in BG2 (unless you're playing BGT, or EET mods).
The books also exist in the game codes of the other games in the series, even though they do not show up in game and can be obtained through the console.
Baldur's Gate II has different ways to increase attributes.
|Manual of Gainful Exercise||Strength||Candlekeep Catacombs||BOOK04|
|Manual of Quickness of Action||Dexterity||Thieves' Guild||BOOK05|
|Manual of Bodily Health||Constitution||Pirate Cave||BOOK03|
|Tome of Clear Thought||Intelligence||Ramazith's Tower||BOOK06|
|Tome of Understanding||Wisdom||BOOK08|
|Tome of Leadership and Influence||Charisma||Gnoll Stronghold||BOOK07|