[molenick]

I think book collecting is to some degree analogous to what happened to stamp/coin collecting. An aging collector group, young people who in many cases do not come into contact with the physical object (not that they don't read, just that they don't need a book to do so), and the realization that many items were considered "scarce" only because you had to buy them from a handful of dealers. With eBay and AbeBooks, you can pretty much get any book you want now. Maybe not in the condition you want, or in the edition, but for any book published since ca. 1970, probably 95% of the books you are looking for.

Like stamps and coins, the very rarest books will still be in demand and command high prices in an auction. But it's based almost entirely on rarity. You will pay more for better condition, but it's not like a Putnam team history in "like new" condition will sell for 100's of times more than a nice looking but technically very good copy. Many of the books I paid a premium for because of scarcity, edition, or condition are worth the same (or less) than they were 30 years ago (if I could sell them at all).

It may not be an exact analogy, but it is an area of the hobby where there has been mostly a decline in value (especially if you take inflation into consideration). There simply is not enough demand to support the supply. There aren't a lot of stories of coming home from college to find that your books were thrown away and now you are chasing your childhood collection.