My general preference these days is non-fiction. For discovery methods see this comment: https://news.ycombinator.com/item?id=29609479
Generally my problem is far too much content and not enough time, rather than the reverse.
Online content seems to have rapidly diminishing quality. Search and discovery tools are increasingly disappointing.
More on general "finding stuff" here: https://tildes.net/~misc/szx/what_tips_or_tricks_do_you_use_...