This book is a fantastic resource for anyone wanting to make their monsters more unpredictable and mysterious. Tables upon tables to spark the imagination. I especially recommend the " O is for Ordinary" entry to give old favourites a bit more oomph.

As an example, I rolled up an angel with insectoid features and the ability to spit acid - and from that followed the creation of Xkrrrg the Many-Eyed God, lord of all that crawls and skitters for my campaign world.

And the whole thing is system-neutral, allowing you to use it with whatever system you enjoy. Given the modular nature of monster abilities in D&D 5e, for example, it's extremely easy to translate whatever table results you get into the game. And the same is true for most OSR systems as well.