It's true (or at least, widely reported) that the built-in iSight's behavior in scanning barcodes varies from model to model, and even from machine to machine. This is why I advise starting your barcodes very far from the camera, then slowly moving closer, so you can find your individual machine's sweet spot.
That said, scanning on internal iSights has gotten better, not worse, with revisions. Scanning on the first generation iSight iMacs was possible, but not exactly a pleasure. My last-generation Core 2 Duo MacBook Pro scans as well as the external iSight scanning in Delicious Library 1.0 (being that the new research on scanning with the internal iSight ended up making scanning with the external iSight 200x more efficient).
So I have to imagine the new-new MacBook Pro scans even better, but I don't know. I guess we have a couple of machines coming for winning that Apple Design Award, so I should be able to give you a first hand accounting sooner or later.
Books usually scan pretty easily. Make sure you are scanning the correct barcode. Mass-market paperbacks typically have a useless barcode on the back, but a good barcode on the inside front cover.