I've used WebGL for years in my web projects - but I wanted something that would give me a way to tune my skills instead of just reading tutorials or books .... and this hit the nail on the head!
It's both a guide for beginners ...but also something you can get teeth into something - the few projects at the beginners have training wheels for beginners while the later ones..... really let you push yourself. I'm still working through the projects... my plan is to do a couple a week so I can get them all finished by xmas :D
Also lots of extra tasks and things to try ... so you won't get bored!