Rel said:
The value to a given Wizard would be the cost of a scroll of each spell that the book contains that he doesn't already have but definately wants.
Might wanna check the math on that system. Low level spells would be underpriced and high level spells would be overpriced. Remember, scrolls cost what they do because they are spell *completion* items. A spellbook is a spell *preparation* item.
It costs a wiz [3.0; not sure about 3.5] 100 gp per page to make a "backup" of a spell he already has, so I'd use this a a basis for pricing out the book. It would be reasonable to include modifiers (+10% to +100% would be my advice) for "Name" and rare or unique spells.
As to having to copy the spell before using it -

- never read that rule anywhere. I did see one that said it was DC 15 + spell level to use another person's book. Also, keep in mind, if you make the book yours (e.g., prepare spells out of it over a prolonged period of time) it won't be "another person's book" forever.
Example: I acquire the 3.5 DMG. Things in it are largely familiar, but subtley different enough to cause me the occasional problem when preparing an adventure (flubbing my DC 15 + rule level check). After a while, though, the spine on my 3.5 DMG is cracked and the pages dog-eared, and I am preparing 3.5 adventures with ease.
