Just got the game. The guide had the wrong levels for the begining of high-level abilities. Here are the ACTUAL levels at which you get high level abilities:
Fighter/Barbarian: 20
Ranger/Paladin/Mage/Socerer: 18
Druid: 15 (they got 1 right)
Cleric/Monk: 22
Thief/Bard: 24
Heh, that's exactly one level after the SoA XP cap.
[url="http://www.sorcerers.net/Games/BG2/SpellsReference/Main.htm"]Baldur's Gate 2 Spells Reference[/url]: Strategy, tips, tricks, bugs, cheese and corrections to the manual.