Since we are on the subject of children’s books, I would like to talk about some other books that my son reads by himself. By the way, my son will be seven soon. His favorite is the Magic Tree House book series by Mary Pope Osborne. These chapter books target kids from kindergarten to 3rd grade. Each book is roughly 80 pages, written in simple sentence format, so it is pretty easy for kids who start to read chapter books. The stories are entertaining and full of imagination.
Chapter books - http://www.randomhouse.com/kids/magictreehouse/books.html
Another chapter books that he likes are the Magic School Bus series. They are a series of science adventure books by Joanna Cole. I like this series a lot. They are fun, entertaining and very educational. I even learn something new, such as the recycling process. We learned about the Magic School Bus from watching the TV shows. It is currently showing on Discovery Kids.
Chapter books - http://www.scholastic.com/magicschoolbus/
If you have kids who start reading chapter books by themselves, I would highly recommend these two book series. For me, I prefer the Magic School Bus book series as they are more educational.