The sad thing about book collections is that they're not worth buying for book antiquities because chances are that most won't sell at all and the few games might just be worth a few $ so most just end up in the recycling bin once the owner dies. On the other hand that means if you're willing to buy whole shelves filled with books that haven't been preaccessed they can be incredibly cheap.
This, not buying armfuls of books off individual sellers, is how used book stores get much of their stock. Running a good one (not just full of shitloads of Stephen King and Nora Roberts) means going to lots of estate sales.
Also, a lot there for a while but less now that they’re almost all gone, being there with cash in hand to buy the remaining stock in bulk when a competitor/colleague goes out of business.
Sometimes in a good used book store you can spot substantial remnants of some particular enthusiast’s collection, like a whole bunch of German-language original 19th century scholarship on the history of the conquest of South America or whatever. Some improbable number of books on some niche topic, nearly all of which probably belonged to one person (or, sometimes, institution) before landing there.
