Every culture has in its folklore and mythology beings of immense size and strength, as well as other preternatural humanoids great or small who walk among us, serving the divine or fulfilling their own agendas. This book catalogs the lore and legends of more than 1,000 different humanoid species and individual beings, including the Titans, Valkyries, Jotnar, yōkai, biblical giants, elves, ogres, trolls and many more.
A good reference for giants from folklore, although there are some fairies thrown in and a lot of the entries are of individual beings rather than species. But it's still very comprehensive, especially if you don't want to stick with just the Greek, Norse, or Celtic mythos and want the rest of the world to be included. (Granted, the Norse do have the lion's share of the entries, but that's just the nature of their mythology.)
It even has an entry on Dhampirs (yes, the vampire hunters from Vampire Academy) in it. But it doesn’t have an entry on Demeter (Ceres), only briefly mentions her in entries about other gods.
As with the other books in by this author, it is a good place to start when researching new beings.