I've bought and read all 7 Harry Potter books, and about 2 years ago I parked the set in Thing 1's bookshelf and gently urged her to read them. I knew she'd like them. Well, she's just recently decided to listen, and has zoomed through to the 4th book in about 3 weeks. And the other day she asked me if I had any recommendations for her after she finished the series. That was very satisfying.
Even more satisfying, this morning I discovered the first HP book propped open in Thing 2's room. She told me her sister had let her borrow it. I asked T2 if the book was too hard for her (she's 6 and in kindergarten, after all) and she said no and proceeded to retell the plot thus far. Cool.
I can't tell you how pleased I am to have bred bookworms. :-)