I generally rely on others to recommend nonfiction. If someone with a perspective or insight I find challenging or compelling mentions a book I haven't read, I at least will take a look. On occasion I'll stumble on an interview with the author that sufficiently piques my interest.

Also, when I fixate on a new topic I often find that certain titles will be repeated in forums, chats, HN, articles, etc and I make note of things multiple people that seem to know things mention as useful.