I like to think that reading is a reward in and of itself. But when you become a parent, a lot of your beliefs (no child of mine will ever sleep in my bed! no child of mine will eat pasta for dinner every night!) run smack into reality and reality often wins.
My daughter's school signed every child up for an online reading program called Raz-Kids to encourage children to read over the summer. She was given a password and the program was customized to her reading level. Each child's page has books which the child can read (and even record) or listen to, as well as take a quiz about the content upon completion. The books are a mix of fiction and non-fiction and are not, in my opinion, either especially compelling or especially awful.
My daughter picked a book to read, not knowing anything else about the system. When she finished, she took the quiz. She was thrilled to discover that she got "points" for both reading (50) and taking the quiz (150 for getting every question right). You can apparently "spend" the points on something, presumably something virtual, but the mere idea of points was enough for her to beg every night to read more. But I think even without the points she would have been sufficiently motivated by the progress bar which shows her movement from her current level to the next level, the sheer novelty of recording the book and hearing it read back in her own voice, and the satisfaction of taking the quizzes.
These type of rewards straddle the extrinsic/intrinsic divide, in my opinion. The rewards are not tangible but they are visible. She can see evidence of her progress and that is motivation enough for her. At least for now!
What motivates your somewhat reluctant child to read?