Liar, Liar Series by Gary Paulsen

Kevin doesn't mean to make trouble when he lies. He's just really good at it, and it makes life so much easier. But as his lies pile up, he finds himself in big—and funny—trouble with his friends, family, and teachers. He's got to find a way to end his lying streak—forever.

Kevin struggled to overcome his knack for lying in Liar, Liar, and now he's back for another round of mayhem and misunderstandings in this financial comedy of errors. In Kevin, Gary Paulsen has created an appealing teen boy character who is just as human and fallible as his readers.