Discworld

Pratchett, Terry. Feet of Clay. New York: Harper Prism, 1997.
---. The Fifth Elephant. New York: Harper, 2001.
---. Jingo. New York: HarperPrism, 1999.
---. Maskerade. New York: HarperPrism, 1995.
---. Men at Arms. New York: Harper, 1997.
---. The Truth. New York: Harper Torch, 2001.
---. Thud! New York: HarperCollins, 2005.

Terry Pratchett's shape-shifters cover a wide range of books but basically come down to two beings: vampires and werewolves. Technically, the Librarian could be included, but because that was a one-way transformation, I exclude it (even if magic could be used to change him back to human). To some extent the witches' Borrowing may fall under a broad definition of shape-shifting as psychic shape-changing, but because it involves the witch's consciousness riding, but not overtaking, an animal's, I'm excluding it as well.

The above list is unfortunately not completely inclusive, as Pratchett has vampires and werewolves in many of his books. However, the seven in the list are the ones in which such beings play a major role, rather than minor background roles.

Pratchett's vampires fit many of the stock traits: vulnerability to sunlight (can be ignored with full coverage clothes and broad brimmed hats), blood drinking (although this is really a thirst for power and can be beaten with willpower), and shape-shifting (into a group of bats). The last power is different depending on gender--males retain their clothing upon becoming human again, females do not. Sally explains this in Thud!. Pratchett's two most common vampires are Otto von Chriek (The Truth) and Constable Sally (Thud!), although others appear for brief times, especially in The Fifth Elephant.

His werewolves are very aware of their dual nature, with Sergeant Angua being the most introspective of all. Through The Fifth Elephant and Thud!, she describes the werewolf experience in both general terms and in relation to vampires. Werewolf shifting here only includes two forms (human and wolf), does not allow for retention of clothing, does include regeneration and silver vulnerability, and unsettles the domestication of canines. On the last point, Pratchett constantly refers to the thin line between wolf and dog, both in character thoughts and Sgt. Angua's behavior. There are other werewolves in the books, but I have focused on Angua here because she is the only recurring werewolf and the one from whom readers get the most information.

The novel Masquerade does introduce some Elf shape-shifting through glamour, but this is more or less limited to the one novel. This form of shape-shifting appears to be more illusory that real change in that it can be disbelieved and seen through by the strong-willed (such as Granny Weatherwax).