How are you going about it? What I mean is, do you let them choose the books? When our kids were younger I would let them choose the book from the bookshelf outside their rooms. I always held the veto power :), but they got to choose. Since our kids are 3 years apart and had a wide variety of interests, I let them each choose one story.
Some of my daughter's favorites (even before she was old enough to choose) were the I Spy books. I Spy Super Challenger: A Book of Picture Riddles, I Spy School Days: A Book of Picture Riddles, etc. BOTH of my kids always LOVE the Frog & Toad series. And I loved reading them too. They are little short stories that take about 3-5 minutes to read, and there are 4-8 stories in each of the books (there are four books I think). They are quirky and fun. My kids love books that have interesting unexpected things go on, and not that into chapter type books. Even Harry Potter. They just would start playing while I was reading. But if I pull out "The Toughest Cowboy" (which tells the story of a rough tough cowboy who adopts a..... poodle) they crack up and want to hear it over and over. They love Arthur books too. They'd beg me to read the one where DW tries to scare the boys with a fake UFO during a campout! Why? Because they loved the line where the dad tells the boys it's time for bed, and the boys say "He said it's bed time, but he didn't say SLEEP time! " They also used to love The Grinch (and no, it didn't need to be Xmas season), because they thought the drawings of the little dog were hysterically funny. Or Dr. Suess's "Pale Green Pants" story...
So, I would say take a look at what kinds of books you are reading for them. They are far more likely to enjoy something that sends YOU over the deep end, than a cute little moralistic story that you might prefer to read. Although, I always tried to work a deal with them, if I felt up to reading alot that night, and I would read MY choice first, then theirs.
Sometimes I would let them read "a page" here and there too.
Try changing up your material... and see what happens.