IMHO the reason is that when you level up, your primary skill (wizardry/alchemy/psionics/divinity) may not be sufficient to learn the spell. However, later when you do reach the threshold, then the book is readable. Then when you read the book and learn the new spell, you often get more spell points, school goes up and if you're really lucky the primary skill too. The key numbers are 15/30/45/60/75/90 for level 2/3/4/5/6/7 spells - Wolfie has an excellent spell availability spreadsheet to calculate which spells are available..
|