Well, spellbooks are not scrolls, since scrolls require exp AND materials to produce, and they are consumed after casting, the spellbok has the guidelines to casting a spell, but that doesn't make it possible to say it is a scroll, it doesn't have the materials spent already...
If you can cast a spell from a spellbook as if it is a scroll, it also means your spell will disappear from the book, that you have to provide the materials and pay an exp cost to inscribe the spell to the book... and at last, it also means that you can memorize a spell from a scroll, what seems to be against the rules... (you gotta learn it, write on the book -- thus loosing the scroll).
Anyway, I would love to have a spell cast from a book, but would make it very different from a scroll, with lot of time required and also the components needed. After all, if you book is a scrollbook which doesn't loose the spell, what is the point with the existence of sorcerers and scrolls?