Start a book club with your kids.
Hang up a piece of paper somewhere in their room where they can keep track of all the books that they read or that are read to them each day.
Set a certain number for them to work toward, and once they've reached their goal, give them a special reward. (We have our goal set at 15)
I used to use toys and treats to motivate my girls, but lately I've been raiding the Goodwill around the corner and buying all the children's books I can get my hands on since they're only 25 cents a piece. I wrap them each in wrapping paper, and each time their goal is met, they get to choose which book they'd like to unwrap.
They treasure these books because they are their very own and they earned them. So far they've earned three books each and are working toward another one.
I highly recommend trying it out with your family!