When I was little most of my books came from jumble sales.
For the Americans (and the more middle class) amongst you, these are a kind of yard sale, but usually held in a church hall and contributed to by the local community. Picture long trestle tables heaped high with various cast off clothes and bric-a-brac. They had their own particular smell, those jumble sales; not just from the old and sometimes unwashed clothes, but also from the feisty little old ladies who would barge you out of the way if their gimlet* eyes spotted a bargain.
Let me tell you, old ladies elbows are hard, and you don’t want to be on the receiving end of one.
As well as the mountain of old man’s pants, there was, in the far corner of the room, near the hatch that served lukewarm squash and tea so strong a sugar lump would bounce off it, an unsteady table housing a stack of musty and torn books. Now, most of these were Reader’s Digests that nobody wanted, but every so often I would strike gold, and find an Enid Blyton or a Frances Hodgson Burnett.

Kit-in-the-Candlestick – Amazon UK