For baking, I have this. After buying it, I've given away all the rest of the books I had. I have the digital version on my iPad. It goes with me everywhere.
I have almost every book on cake decorating out there. One that has almost every technique explained in a concise manner is The Contemprary Cake Decorating Bible, Lindy Smith. 150 techniques, 80 projects.
Besides that, I've been buying all the craftsy classes. There's ine with Colette Peters that's amazing.