Ooh! A new book thread! We're always in desperate need of new suggestions, so I'll be following this with interest.

DS6 has just (today!) finished the HP series. I noticed that he slowed down a lot after book 3, and I think he dealt with some of the darker, scarier themes by reading more shallowly in the later books. He rereads a lot, so I'm sure he'll get new things from them in subsequent readings.

The Mad Scientists' Club series by Bertrand Brinley was a big hit with DS. Mad Scientists' Club books It features a group of boys who use science as they get in (and out of) mischief. My library doesn't carry them, but Amazon has them, and they've been worth every penny. DS has reread them several times.

The Alvin Fernald series by Clifford Hicks is another favorite here.
Alvin's Secret Code and The Marvelous Inventions of Alvin Fernald are two of DS6's often-reread favorites in this series.

Dragon Rider and Igraine the Brave by Cornelia Funke are two others that DS has really loved. I think Dragon Rider is his all-time favorite book. Dragon Rider features a young boy going off with a dragon as it tries to find a safe place for dragons to live. Lots of magical creatures, very sweet story.

The Sisters Grimm - All of these books have been hits with DS.

The Thirteen Clocks by James Thurber was another recent favorite. It's on my shelf to read now that DS enjoyed it so much. I've heard many people say it's one of their all-time favorite children's books, so I think I'd better read it!

Simon Bloom, Gravity Keeper and its sequel by Michael Reisman - As I understand it, the book combines magic with science (especially the laws of physics). That's always a winning combination for DS.

I'd go into more detail, except I haven't read all of them yet. I've given up on previewing books as there's no way I can keep up and still have time to read any of my own books (or do much of anything else).