For the longest time I could remember, even before I got into Dungeons & Dragons, I always loved the idea of being the monsters for a change. Taking on the role of a mighty golem or brooding vampire seemed appealing to me, and the limited choices of races in most official sourcebooks seemed at odds with fantasy settings populated by all manner of intelligent beings.
Official sourcebooks' attempts to do this resulted in mixed success. The truth is that a lot of monsters had abilities which would be game-breaking in the hands of players, or in some cases the options were made weak so as to discourage too much deviation from the Tolkinesque Player's Handbook races. While working with Oslecamo on Min-Max Boards on designing monster-based classes for 3rd Edition, I came upon a realization: the majority of monsters both original and drawn from folklore were known for a limited set of abilities as defining features. Harpies are known for being winged sirens whose melodies could entrance people, not their +3 natural armor bonus and racial hit dice.
Taking this idea, I boiled down the abilities of several popular monsters into a smaller framework, getting rid of extraneous mechanics. Eventually I designed Playable Monsters, Vol. 1: Fantasy Iconics & Mythology for the Pathfinder Role-Playing Game. Then I made a version for Old School Monster Classes. Both proved to be popular sellers, and now that 5th Edition is out, I figured that making a version for that game would be a good idea, especially given the fact that monstrous races don't really exist as an option in most official or third-party material from what I've seen.
Here's the OneBookShelf link to the title. It was tiring yet worthwhile to make. If PC-friendly harpies and vampires sound right up your alley, then I hope my book brings more fun and excitement to your gaming circle!