A series about a king and 2 of his companions taking a quest to find some relics or gems or something. I read it in elementry school, around 2004-2008, but it could be older than that. There's a dark lord and some ultimate evil, but I don't remember many specifics. I think there was also a dragon for each gem? Not Eragon, though. It's medieval fantasy I think, like kings and knights and magic.
I do remember 1 thing that, at least I hope, would set it apart from most other books. In the book, the characters were often presented with puzzles they needed to solve. Then, after a description of the puzzle, it would have a small illustration of the puzzle layout on the page below it.
One I remember clearly - the main character is presented with 8 squares, made with sticks. Each square is made of 4 sticks, and some of the squares share sticks with the ones next to it. Inside 7 of the squares are scarabs, or beetles of some sort. The person presenting the puzzle then tells them to remove 2 sticks that aren't touching, and make it so that no scarab is released from the frame, and no square has more than 1 scarab - or something along those lines. Then it had a picture that looked like how it was described.
EDIT Thinking about it more, he may not have been a king at the start of the series. I think the main character became the king in book 1 or 2, but I may be wrong.