Anything I enjoy doing is worth my time. I enjoy reading non-fiction when the topic is interesting and the writing isn't terrible. It's usually such a small investment that if I'm interested in the topic I can take the risk in picking up a book about it even if I later discover that the writing is horrible and don't finish it. For books that are obnoxiously/unreasonably expensive I'll find a digital copy or make sure it's recommended. It is sometimes useful to be able to flip through the book first though just to make sure that it actually covers what I want to know and to get a feel for the depth/level of experience it's written for.