it's about 50/50 between
going into a bookstore and picking out whatever looks interesting, writing down the name of the book and author, getting some more context about the book or skirm through reviews and buying it.
or just looking up "books simmilar to x" looking through recommendation threads on piefed/lemmy or such.
the "checking the reviews" part is especially important for non fiction, i'd rather not waste time and money reading about something that the author has no actual knowladge in

huh haven't used that platform in years, guess I minght as well delete my account