I wish I had a bunch of ideas to offer you. I was doing the same search a few years ago, and didn't find much. I second MM's recommendation for "The King's Chessboard" by David Birch. My DS6 and DS8 still read that book from time to time.
I just looked on our library's website, and there were a couple books that came up. I'm unfamiliar with them, but here goes, "Mort the Sport" by Robert Kraus:
Mort's attempts to excel at playing both baseball and the violin make him so confused that he decides to take up chess instead.
And "How to Survive a Totally Boring Summer" by Alice DeLaCroix:
When Randall and his friend Max start a chess club in the park to keep busy during the summer, there are unexpected benefits for the community.
I'm not sure if you're interested in a basic book on chess, but "The Kids' Book of Chess" by Harvey Kidder was one my kids enjoyed when they were first interested in the game. It has some explanations of the pieces (not just the moves but what each piece equates to -- like the pawns being the serfs/foot soldiers, etc...), and some basic info about attack and defense and a description of Blitzkrieg.
As far as Harry Potter, it does have wizard's chess in it, and frankly when DS8 (then 6) first read it, he was most fascinated with the scene in the first book in which chess plays a big part. I wouldn't say that chess is a big theme in the series, though. And you'd have to make the call if your DS is ready for it. Frankly, I long for the day when I don't hear, "Hey, Mom, in the xth book of Harry Potter..." from one of my boys. *lol*
Good luck in your search.
