German children books

Hey there! Can anyone recommend some good German children books?
I wanted to give something special to my best friend for Christmas. She's studing translation and loves children books, I found this site (thalia) but there are to many titles to choose from so I'm kinda lost.
I'm sure she has already read the Her Bello trilogy and Zugmaus by Uwe Timm. Something inedit would be better but classics will do too.
Thanks in advance to everyone who could help!

cross-posted