Like may other people, I read this when I was quite young, along with many other Bradbury books.
Unlike many other readers, I didn't really love this book when I was a kid - I like Bradbury's sci fi more. Re-reading as an adult, I feel I understand why: this isn't a book for kids, it's a book for adults feeling nostalgic for the impatient hopes of 'boyhood' (and that is 'boyhood,' not the more generic 'childhood') It's a very time-and-place specific boyhood, too - obviously rooted in Bradbury's own youth, but yes, probably, as previously noted, owing as much to Norman Rockwell-esque visions of Americana as to reality.
That said, I enjoyed it, this time around. The themes of boys wanting to rush through (or skip) boyhood, of men wanting to recapture the vitality of youth, of choosing whether you will grown into a good or an evil person... I felt that they're handled well; and I do really enjoy Bradbury's writing. And boy, that circus is creepy!
It's not perfect... I didn't feel that all the metaphors worked perfectly on all levels, the father finding all the answers in the library, although very cool, was a bit deux-ex-machina-y, and there are other problematic, dated, aspects to Bradbury's worldview. Overall, though, a book worth reading.