ok heres the rest of my critique,
1. fix the about the authors page, now. make the link right, fix spelling and make the bio's as well written as the book, i really wasnt impressed with that part,
2.whats up with that insert sub-header here thing ?
3. general polish and mabey some diversity between pages.
4.make the guestbook on the site, not on a link
5. those spoilers are a little iffy, you may just not want them at all
6. i got the feeling the authors were young, but 12 and 13, thats impressive!
7. i have the site in my quick links bar so im going to go back to it, im actually really interested.
8. overall i think its very good, mabey you should check out some other authors sites to get ideas to make yours more proffessional.
i hope my comments helped