1. GUILT. We receive an awful lot of review copies of books, more than we could possibly review, and we have been reviewing fewer books recently. This is because I (Aaron, FR's primary reviewer) have had work and family conspire to reduce my free time, and I've been devoting more of the free time I have to my own writing (which also means most of my reading lately has been short fiction, as I try to teach myself how to write short stories). We are well aware that the publishers sending us these books are on tight budgets, and we feel we either need to stop accepting review copies or find some way to help publicize the books we receive even if we're not going to review most of them. Many bloggers do "books received" posts for this purpose, but the Battle of the Books seemed like a more interesting and unusual way to promote all these books and their authors.
2. NEW AUTHORS. At Fantastic Reviews, we love to publicize talented new authors. We've been able to do that recently as to short fiction with our Story Recommendations of the Week, but we haven't been doing as much to spread the word about novels by new writers. The Battle of the Books will prompt us to discuss new writers whose books come to us, and will give them at least a fighting chance at being reviewed.
3. POSITIVE REVIEWS. Having some of my own stories published this past year has taken away my enthusiasm for writing scathing (or even lukewarm) reviews, for two reasons. First, I've been learning just how difficult this writing thing is. Second, I worry that readers may take any negative comments to mean I think I could have done better. Through the Battle of the Books, I'll end up mostly reviewing books I really enjoyed, while the negative responses will be limited merely to a paragraph on why a book's opening pages didn't grab me.
4. LEARNING EXERCISE. I've focused my writing on short fiction so far, but in the present market, novels are where it's at. If I'm going to stick with writing, before long I need to work at novel length. A strong opening is crucial for selling a novel and for attracting readers. So reading the openings of many different books should be a useful exercise.
5. SOMETHING DIFFERENT. It just seemed like fun.