As the Princess gets older we're reading chapter books together - it's so much fun to revisit the ones that I've loved. Plus, it gets me out of reading the encyclopedia ones she loves so much; forest fires, earthquakes, killer spiders, dinosaurs, pyramids and mummies, insects, mammals, and tsunamis is just a fraction of her list of "must reads".
Reading List So Far (that I can remember, which means this list is suspect and incomplete...):
Betsy-Tacy Series
All of a Kind Family
Lulu and the Brontosaurus
Geronimo Stilton (she is OBSESSED with this series. She's listening to it and we're reading books together)
The Wizard of Oz
Paddington Bear
The Magic Treehouse
James and the Giant Peach