I use two filters:

1. I only buy (and read) a book that is at least 10 years old. For me, 10 years is enough for other people to figure out if a book is worth to read. 95% of all books that are today's bestsellers turn out not to age well. Because none of the books are new, I can usually buy them used.

2. I'm only buying it if I'm pretty sure I'm going to read it. I always read the digital preview and sometimes (if available) I download the digital version which I read for a while. I want to know if I'm going to read the book before buying it.

Yes, 100% aligned on the old books. I haven't purchased a bestseller or anything "new" in some time.

I stopped buying books on my mother languages (russian and ukrainian) because our culture goes south and certainly no great works is coming on these languages. Even youtube on this languages completely turned into shitshow. But there in so bookshop in Ukraine which sells english books. So my only source of books is torrents. And I will never buy ebook again because the one I bought per $20 losted with my HDD and the e-mail it was sent is abandoned now - so I can't prove I deserve to be sent another copy.

I keep a running list of books I want to pick up next, split into types of books and a separate list of hardcovers.

This is a list I keep separate from any one store, and I reorder it until it settles into a pretty good order. I have been really disappointed by cart functionality and have even lost some items etc.

I do tend to order in batches but mostly because I wait for sales and they usually cover more than one book I want.

Slow shipping is OK with me.

Some of the smaller sellers are fun. I like that Wayne's Books throws in a cool little business card. I like that Brett at Pigames.net remasters vintage game books.

I keep a chaotic list of books that I see mentioned and look interesting in Obsidian. If on phone or iPad I screenshot the goodreads page for the book and put it in an album "book".

Now and then I check some of the books reviews on goodreads (the text reviews) and or a couple of them or, if I want to treat myself, 10 or 20 of them. To be, receiving 20 books is the definition of happiness, and one of the few things I will happily splurge on.

Most of the books I purchase are used “vintage” out-of-print hardbacks, usually 50-150 years old. Normally the cheapest G/VG, but sometimes I’ll buy what is referred to a “reading copy”. Often I build a pile of to-be-bought on Bookfinder…sometimes I make a single immediate purchase and ignore the list, but sometimes I just get sick of seeing the list and order a bunch to shorten it. I do not try to order several books from one bookshop, even if they offer a discount. My interests are too specific to expect that a single bookshop will have more than one book per order. Publishers are irrelevant unless I can get a 1st ed cheap.

Delivery times are normally irrelevant. I try to keep a steady trickle of vintage books entering the house. Christmas every week! Since most are in the public domain and available for free online, I often skim the online copy to determine whether a physical vintage book warrants the shelf space.

Yes to the steady trickle of vintage books! I too spend a considerable amount of time trying to find titles that are out of print, usually by way of following bibliographies in the books I'm already reading.

If I'm ordering something less than $25 from Amazon, I'll add a book from my to-read list to get free shipping. Usually these are fiction or cheap math/history/science books. For fiction, these are either books I've already read in digital form and want a physical copy of or new releases from authors I'm already familiar with.

Technical books tend to be more expensive, so I usually buy them singly and try to order direct if possible. If I'm doing research on a specific topic I might buy many, but I usually do one at a time. I've found that having too many books in my "to-read" stack gives me a kind of anxiety that stops me from making progress.

I go to one of my local indie book shops most weekends and always grab something. Sometimes it's one (sometime two) new releases, sometimes fiction but more often then not non-fiction. Most often it's two or three used paperbacks, fiction 99% of the time. And sometimes still, it's half a dozen oddities from the clearance rack which is where I tempt fate and grab stuff I otherwise would never have looked at twice. I always read the last page of every book, something I've done since I was a kid. It's not terribly informative as to whether it will be good read or not.

On don't buy that much on-line, unless I can't get the books from a local bookshop. My wife used to work for a publisher and loathes Amazon, so we buy new books from Barnes and Noble and used from The Strand, Alibris, or sometimes Powells. The last B&N purchase was a single novel (for the neighborhood book club), the last Alibris purchase was a couple of slim volumes by Philippa Foot.

I don't remember ever leaving a cart open after I left a site.

I prefer books which have rating of at least 4.2 on Goodreads and 1000+ reviews. Higher the better.

Interval is sporadic. If I think it is urgent, then order it immediately, else keep in Amazon wish list and buy when there is a good discount or during sale. If physical copy of the book is expensive, then I consider kindle edition if kindle version is much cheaper.

When I see a book I might like, I put it on my wishlist on Amazon or on my To-read list on Goodreads. Then when I finish the book I'm reading, I take some time to decide what to read next, by looking at those lists, and buy the book I want to read.

This is especially convenient since I only read on a Kindle. So shipment is not a thing I have to think about.

When I think I might want a book I pause what I am doing and search on Triftbooks using the app.

If it is cheap enough, I usually buy.

If it is available but not cheap, I typically let go because there will always be another book I want just as much.