My son is 7 and is a solid reader. He plows through Magic Tree House (no judgement) in a day. He really prefers non-fiction reading, but would love to encourage a deeper love for some good fiction. We have had a hard time keeping interest in other chapter books (as read alouds) long enough to finish them. IE: Charlotte’s Web, Mr Popper’s Penguins, Wishing Chair etc.
Boys love books by Clyde Robert Bulla. I know I sound like a broken record but he has set many a boy on a love-of-reading path for many years including my own sons. Sword in the Tree, Pirate’s Promise, Viking Adventure are all good to start with. Several boys in my library have been devouring books by Jim Kjelgaard and Jean Craighead George of late as well as Freddy the Pig books by Walter Brooks.
I second Bulla’s books and Freddy the Pig. Also Dick KIng-Smith’s books. Would he like mysteries liek Encyclopedia Brown? They are short stories so that might keep his attention.