You're getting all kinds of things wrong here.

1. ISBNs are not sequential. The last digit is a crude checksum. So if 0901690548 if valid, 0901690549 is guaranteed to *not* be valid;
2. The last character can be an X or a digit;
3. ISBNs beginning 0 or 1 are not US books

I suggest you fire up your trusty google and learn some more about the structure of an ISBN before you go any further.