Don’t. But I read, in the areas that interest me, from all perspectives I can locate, garnering clues from the sources and bibliographies in the books I do collect. And that’s what I recommend. I spent 4 years working in the rare/OP book business, (and 10+ in the shiny new book business) and, of course, dealt with such folks in my 60 years of book collecting, esp. starting in 1964. But I don’t do that much any more. I deal with in print books, or from used book sources that don’t require me to shop on line, which limits the selection. I hate to shop on line. So, in theory I could chase down more of them. But I rarely do that these days.Which is probably for the best, given the lack of shelf/floor space still available to me.
Only 130 million? I’m doing better than I thought. Will order 2 more tomorrow. Which brings the total holdings to (best guess) around 30,000.