The Jigsaw Jones Series (ages 7+) Jigsaw and his partner in crime, Mila, solve a series of mysteries both in school and out. This series is great for those starting out on chapter books.
Andrew Lost (ages 7+) Another great series for those starting out in chapter books, these books share the adventures of Andrew, his cousin Judy and their robot as they try to survive being shrunk to microscopic level by the Atom Sucker.
Hank the Cowdog (ages 7+) Ok I find this series on the obnoxious side, but my kids think they're hilarious. Hank is a scruffy, smart-alecky supersleuth of a dog who's head of ranch security. Although clearly not the brightest bulb in the box, Hank and his side kick Drover manage to chase out unwanted visitors and keep things running smoothly on their west Texas ranch.
Box Car Children (ages 7+) A timeless series, this collection of books chronicals the adventures of 4 siblings who solve mysteries. The characters are very heartwarming and wholesome.
The Strange Case of Origami Yoda (ages 8+) This is the first of a two part series about a 6th grade boy named Dwight who expresses himself through a humorous little paper finger puppet. Though comical, the heart of this book explores the changing social dynamics of early tween years.
Dagger Quick (ages 9+) pirates, murder and swashbuckling adventure, what could be better? Club footed Kitto sets out on the adventure of a lifetime to uncover hidden truths about his family and avenge his father's death.
Other books for boys we've read:
howlsage (ages 9+)
Percy Jackson (ages 9+)