Sorcerers do not ordinarily have the ability to read or prepare spells; their class does not give them that ability like the wizard class does.
That doesn’t mean they can’t learn to do so somewhere else. The Arcane Preparation feat from Complete Arcane exists for exactly that purpose, it lets sorcerers and others who cast spells without preparation instead prepare some spells if they like. This avoids lengthening casting times when using metamagic, and may allow the character to meet certain requirements, like mage of the arcane order from the same book.
In the end, then, anyspell is just another way to learn how to read and prepare spells. Clerics can’t read spells from a spellbook normally, either. Same with sorcerers; this isn’t something they get from their class, but instead they get it from the spell and that’s fine.