I added another four sites (and seven lines, bringing the list to a whopping 24 lines) today; BiggerBooks.com, Bookbyte.com, Booksamillion.com and eCampus.com are in version 0.15. just reinstall the script from the latest version permalink.
By now we have certainly started to need a few small features like sorting the table by price, book condition (new or used) and perhaps country/currency and library/store too. But let's not get ahead of ourselves; for one thing, it's bedtime, and for another, the feeping creatures could hurt the user experience pretty badly.
...Next time, Gadget! Next time!