I just discovered, via a customer review on http://barnesandnoble.com, that a boy read Susan Runholt's novel -- The Mystery of the Third Lucretia -- and loved it! Hopefully you will read it and love it too ....
Another series I always enjoy is the Alice series, by Phyllis Reynolds Naylor (who has several wonderful books to her name), and lots of young women -- as well as some middle-aged women, I've heard -- tend to love them. And I was surprised to learn a couple of years ago that boys read and enjoy them too.
(A quick but vaguely interesting note: I have words on the back of Dangerously Alice, which is still in hardcover. If you can find it, something I once said to the author is at the bottom of the back cover.)