Check out Book Wizard by Scholastic. Here you can find books at a level or check the levels of books that you already have. There is even an app that can be put on your smartphone. Simply scan the barcode of the book to get information on level. It is a great tool to have at the library or bookstore. We use it a lot right here in the classroom to check the level of books.
Book Wizard allows you to search by Grade Equivalent, Guided Reading Level, DRA and Lexile. Ask your child's teacher what their DRA level is to help you select books for your child. When you have their independent level, go to Find Similar Books. Click on the books to find more specific information . You can also search by interest by clicking on Search All Books and putting in a topic of interest. To find challenge books to read to your child, click on Search by Reading Level. If your child is a 16 go to level 28 and above. If they are a 28 go to 38 and above. If they are a 38 go to 40 and above.
Lexile.com is another tool for leveling books. The NWEA gives us a lexile range for each of our students. We can use this range to find books in their independent and instructional ranges. On this site you can search for books within their range as well as check the lexile of a specific book.