A summer book should be engrossing, but you should still be able to look up every few paragraphs to check on the kids in the water. It must be eminently put-downable. When your child emerges from the surf with a crab attached to a toe, you must be able to put down the book, remove the crustacean, then pick up the book again and continue without missing a beat. It should be a book you don't mind getting sand or suntan oil stains on. It should be a book you can happily pass on to the person on the next lounge chair after you're done.
Paperbacks are best, but some hardcovers are too good to resist.
On the other hand, if the type is big, it's OK if it's thicker. We have taken it upon ourselves to poll avid readers and book store employees to come up with a list that will get you through the summer, reading all the way. This book has already become a pop culture phenomenon in England, and it's just now available in the States. Bridget Jones is in her 30s, single and neurotic, and is the voice of everywoman as she details her chaotic life. I can actually feel the fat splurging out from my body.