Easiest way to find the reading levels is to look at the back of the books. The classics don't have the reading levels printed on them, but they were written for a general audience, so the reading level would be around Grade 6 for those books. The paperbacks published by Minstrel and Aladdin will have the information at the bottom right corner on the back of the book. For example, The Blackwing Puzzle, the first printing by Wanderer books doesn't list a reading level, but then the Minstrel edition says RL: 6.7 (the book was never issued by Aladdin, but on the Aladdin it would say Ages 8-12). A 6.7 would mean that the book wa written for a reading level of someone about 3/4 of the way through Grade 6 (roughly, someone who has been in Grade 6 from September to March/April).