I came across a couple of interesting articles on the Scholastic website. One is "Choosing Books for a Reluctant Reader" at http://www2.scholastic.com/browse/article.jsp?id=1568. It may surprise you that a librarian recommends the following article, but I think it has merit: "Even Bad Books Improve Reading Skills for Your Child" at http://www2.scholastic.com/browse/article.jsp?id=3746177. Both of these articles deal with the sometimes knotty issue of matching books to kids who are not willing readers. There are lots of choices out there. The two articles will help set you up to find plenty of good choices for your children.
If you have trouble finding books that are a good fit for your kids, a look at these articles may give you an assist. You may want to move on from The Wimpy Kid series, which, like its ancestor, Captain Underpants, is proof that a sassy series can grab the attention of the entrenched reluctant reader. You can search for titles by topic and reading level on the Scholastic Book Wizard, which you will find under teacher resources at the Scholastic site. The search is simple, but remember that the results will focus on Scholastic products, which is only one portion of the vast array of children's books in print.
For parents who are ready for a slightly more challenging but less commercial search, you might like to go to NoveList K-8 under Parents and Teachers on the Mount Prospect Library Website (http://www.oncoursesystems.com/school/webpage.aspx?id=324520&xpage=447664). There are helpful articles and booklists along with tutorials on the best ways to search. You can also get to NoveList through the databases online at Bernards Township Public Library. A chat with the librarians at the public library may also help you and your child to find a good read.
Every book has its reader, and every reader has his/her book. Making the match can be a challenge sometimes, but it's worth the effort to raise a reader.