Because about one time in ten, listing a shapeshifter book as a shapeshifter book is a spoiler. Heh. Even if it does throw a wrench in the works of trying to be an obsessive list-maker. 🙂
Interesting too to see how many different kinds of stories you can tell that involve shapeshifters of one kind or another.
ETA: And lnhammer suggests separating shapeshifters out from one-time, involuntary enchantments. If you can’t change more than once, you’re not a shifter, you’re just under a spell. Which, interestingly, removes most of the potential spoilers from consideration, huh!