Catkid

Catkid is a series by Brian James that follows Catkid who is half cat and half kid through her life.  While Catkid is half cat and half kid the rest of her peers are all kid. 
 
They read much like any other girl book out there except for the cute twist of Catkid's cat side.  In the second book for example Catkid goes to the aquarium. She encounters many difficulties because of this (like when she tries to pack a fishing pole) but still faces normal challenges when she tries to win a contest to collect answers for her teacher.

Scholastic puts these books at a mid-third grade level.  The books are thin, chapters short and there are quite a few pictures through the book.  They are fun and work well for younger advanced readers.