I'm not sure about the issue of getting him to take your suggestions, but I can add a couple of suggestions for fun adventure series that maybe you could just place on the nightstand next to his bed for him to pick up at his will:
- "Time Warp Trio" series (like Magic Tree House but funny and for slightly older boys in particular)
- "Chronicles of the Moon" series (12year old (?) boy and girl go on archeological digs around the world and gather clues to a bigger mystery)
- "Chet Gecko Mysteries" series (a gumshoe-style 4th grade detective, who is a gecko, solves mysteries at school, and has a clever, wisecracking sense of humor)
- "Spy X" series (11 year old twins whose mother, a spy, goes missing and they have to solve riddles and codes to gather information and eventually find their mom)
- "Chasing Vermeer", "The Calder Game", and "The Wright 3" by Blue Balliett (Smart kids solve riddles, mazes,coded messages, and other clues as they work to solve mysteries related to painting, sculpture, and architectural masterpieces)
HTH!