Saeviomagy
Adventurer
Patryn of Elvenshae said:Where's that rule, Saev?
"A wizard can use a borrowed spellbook to prepare a spell she already knows and has recorded in her own spellbook, but preparation success is not assured. First, the wizard must decipher the writing in the book (see Arcane Magical Writings, above)."
The key phrase is that you can use the rule to prepare a spell you already know and have recorded in your own spellbook.
This is present in the SRD.
If someone wants to check an actual PHB, great. I'd be really relieved to find that this rule is in error.