Let them know that you are truly interested in their thoughts and feelings that these books invoke. Set up a reading incentive program. I have one for Brendan and it works wonderfully. He is very incentive motivated. It always feels good to reward them for a job well done.
Books make an excellent reward.
Keep a book handy in the car and in the bathroom. This encourages reading. Begin collecting books for your home library. It is good to have a collection. Make sure that you keep their favorites in this collection.