-and this post is also part of my Helluva Halloween challenge
Another non-werewolf shapeshifter that comes to mind that I like is:
Odo of Star Trek's Deep Space Nine tv series
For his appearance in book form, there are a slew of non-canon Deep Space Nine novels released since 1999 to present.
As you may guess being in the sci-fi world, Odo is an alien. He is pictured here in humanoid form but when in his natural state which is a sort of goo he resides in his bucket.
Have you come across any alien shapeshifters in your reads? Do tell.