We read these aloud with our 8 year old (this and Chasing Vermeer) and loved them. Fun, smart mysteries for kids, set in Hyde Park, Chicago. The children in the book are 6th graders, and I think these might be at too low a reading level for many book-ish 6th graders, BUT would be great for reluctant readers that age because they have codes to crack, including illustrations, and they are fun. The relationships between the kids are nicely complex and have some tension, without being the whole story: so they have a balance between action and relationship.