A few you might check out:
The Humphrey the hamster series
The Zoey and Sassafras series
The Secret Explorers series
Alice in Wonderland
Some Beverly Cleary books
Many of the DK nonfiction books
The Humphrey the hamster series
The Zoey and Sassafras series
The Secret Explorers series
Alice in Wonderland
Some Beverly Cleary books
Many of the DK nonfiction books
And, Terry Pratchett: Wee Free Men
Of course all the rest of Terry Pratchett is there to grow into.