It can be difficult to find books that have high interest and are also written at a level so that children with reading challenges can enjoy them. A good starting point would be to talk to the special education teachers, reading specialist, and librarian at your child's school. In addition to recommended books, you may also want to ask for suggestions of children's magazines. Magazines tend to have appeal for all students and have many advantages for struggling readers because of their interesting and current topics, large number of graphics, short articles, and "adult" look. Also consider asking the librarian for suggestions of books of poems. There are some hilarious contemporary poets out there whose poems have mass kid appeal. And because poems, like magazine articles, are short, they are instantly gratifying and provide an immediate sense of accomplishment for all readers.
You might also look into high interest-low reading level books (hi-lo books). Find helpful information about hi-lo books and booklists.