We are, apparently, living in The Golden Age of Photo Books. New books are published almost every day by photographers known and unknown. Websites exist solely to showcase them (Josef Chladek for example).
I have my own fair share of photo books: currently about eighty of them. (It used to be more but I was running out of shelf space so I donated about 40 of my least-favoured ones to the charity shop.)
The average cost of a photo book these days is about thirty quid. Value-for-money varies: a few are excellent; many are mediocre. It’s hard to know what you’re getting if you buy on Amazon since you can’t leaf through the pages like you can in a “Real” book shop — a lot of the time you’re taking a punt.
What I’ve found recently is that many of the books getting coverage on the internet are by photographers who are currently en vogue with “Curators” and the cognoscenti (They’re out there), not necessarily the best ones. This has led me to buying some dross which ended up in the aforementioned charity shop, though you can sometimes find great books by little-known photographers.
When it comes to selling your used photo books, most of them will be all but worthless. The only ones with any resale value are those by big-name photographers, preferably from a limited edition. Some people buy multiple copies of their new books and store them in the hopes of making a profit down the road. Personally I buy books purely for enjoyment.
My book-buying habit has dwindled to a near-stop though: I have enough to keep me entertained for the foreseeable. I’m also trying to spend less and accumulate less in general.
To this end, I would be happy with electronic photo books: the technology is there already. I suppose it might be too easy to pirate images though — I suspect that’s why they don’t exist*, so for now it’s dead trees and diesel to get them to you.**
*Update — yesterday I bought two Kindle cartoon books by Roz Chast. The reproduction was adequate and I could view the illustrations in full colour on my computer monitor. I don’t see why you can’t buy photo books this way.
** I made my own Kindle photobook. It was quite easy.