Where do you find reading suggestions?

I use Goodreads

I use Blinkist for summaries and when I like something, I read or listen to the full book. (No affiliation with Blinkist, just a fan.)

I usually find recommendations on Twitter, more or less randomly, from people bringing them up in conversations. Same goes for podcasts, where many guests recommend books that made a difference. I usually note down the name of the book the moment I hear it.

I have started consolidating the books I always recommend other founders to read on my blog in a section called the Bootstrapper's Bookshelf (full disclosure, these are affiliate links). I regularly add new books to that list after I read them and find them recommendable.