Castles & Crusades Players Handbook is the best Kindle supported RPG around. The first monster manual for the set was Monsters & Treasure, which contains most of the standard RPG monsters (centaurs, trolls, dragons).
Classic Monsters has the stranger monsters. This is just a selection, there are many more: algoid, ascomoid, aurumvorax, babbler, behir, berbalang, boggart, carbuncle, catoblepas, crypt thing, dark creeper, demilich, derro, disenchanter, firbolg, flumph, grue, huecuva, keck, korred, mephit, mudman, nilbog, ogrillon, peryton, phoenix, revenant, russet mold, selkie, tarrasque, thoqqua, vargouille, volt, xsayarsa, yeti.
The write ups for each monster work well, in the clear C&C format. The book also includes pictures of most monsters, but in a slightly flawed way -- all the monsters of a particular letter of the alphabet are described with stat blocks and descriptions. At the end of all the "A" monsters, there is a series of pictures for the A monsters. It isn't always clear which pictures go with each monster. For example, at the end of the T's, there is a picture of some sort of panther centaur, but no centauroid monsters are described in the T's.
So, there are a few minor flaws. But this is a great list of hundreds of monsters for your encounters. Recommended.