A close friend and I were wondering, if a Magus/Wizard share a spell from both of their spell lists, how it is cast in regards to usage and preparation. Say, a Magus has a spell in their Wizard spellbook. Can it be prepared and cast as a Magus spell?
Here's a relevant quote:
"A magus can learn spells from a wizard’s spellbook, just as a wizard can from a magus’s spellbook. The spells learned must be on the magus spell list, as normal. An alchemist can learn formulae from a magus’s spellbook, if the spells are also on the alchemist spell list. A magus cannot learn spells from an alchemist."
–Pathfinder Advanced Player's Guide
Best Answer
Ambiguous. You'd at least be able to copy it over pretty easily (though that'd cost a bit of gold), thus having it in both formats. You could also prepare it via the borrowed-spellbook rules, and deciphering the writing would be automatic since you're the author, so you'd be able to do it with a spellcraft check (DC 15 + spell level, one check per preparation, on failure cannot prepare that spell again until tomorrow). However, to just prepare it directly, skipping that spellcraft check, is not clear from the RAW.