I was hoping someone would mention Animorphs :) The Andalite Chronicles definitely merits another read as well.
My next jump was to Mossflower and Redwall!
I've also reread all the Redwall books as an adult and it was amazing. Be aware that they didn't make audiobooks for all the books so if you're planning on listening, you'll have to read at least some of thing in book form.
Also they didn't make hardcovers for everything which is annoying if you're collecting them to sit on a bookshelf.