(Spoilers and quotes abound within--if you haven't read the Narnian books and don't wish to have them spoiled for you, go no further.)
I was one of those kids who sort of grew up with the Narnia books (my older brothers loved them and we have a well-worn boxed set to prove it), but never actually read them until I was a pre-teen. Then I made the mistake of reading The Last Battle first (because it had the picture of a unicorn on the cover), and read the rest of the series out of order before coming to my senses and reading them from the beginning.
Since then--well over 10 years ago--I've read them several times from beginning to end. Each time I see something else or remember parts that I've forgotten about, and start wanting to use words like 'delicious' and 'beastly' and 'thrilling' more often and call people 'a brick'. (That's a good thing, apparently, to be a brick.) Recently I got an omnibus version of the series that's about the size of my omnibus of Lord of the Rings, and have been remembering why I love these books so much.