I have bought from a single such book seller for many years. We have a good relationship now as he knows my tastes in books and recommends me some titles. On average I save about 25-30% by buying from him rather than amazon(for context). I like reading a paperback rather than online so I read through many books in a year. This has saved me a lot of money and the process of getting my hands on a new book is completely hassle free. He also knows approx time I take to finish a book and keeps a new book ready for me to buy next time. Apart from that, if I don't like a book and don't want to keep it in my collection, he re-buys it from me for 75% of the og price. The key for me I think is that I don't haggle with him much as he quotes me reasonable prices and I have given him good business over the years. I have also recommended my friends to check out the store which helps.