If you are a compulsive HumbleBundle buyer, you may already have it! If not, it's great. I didn't finish it, but I read through maybe a third of it, and that was enough for me to feel comfortable enough to learn the rest of it as I went.
I wouldn't call myself an expert, but got far enough to publish a game (Puck Fantasy, available here: https://www.lowkeyart.com/puckfantasy ), so I'd recommend the book!