One thing I really like about the Tag Reading System by Leapfrog is that the books compatible with the Tag reader can be enjoyed just like regular storybooks -- and cost about the same as the regular hardcover versions.
Take Po's Tasty Training, Tag's Kung Fu Panda activity storybook. 3Po and Jammy love Kung Fu Panda but are too scared to watch the movie. So they like reading Kung Fu Panda books; they get the story without the scaredy. Po's Tasty Training isn't available on Amazon; it seems to be an exclusive Tag product, so they could enjoy it even if they didn't have a Tag (or if their Tag's batteries were dead, or if it had gotten thrown in the toilet).