Just because a book doesn't look like much doesn't mean it can't be incredibly valuable. With a little luck you can grab these interesting oddballs for far less than they're worth.
Buying and selling books on Amazon and other marketplaces can be a profitable venture. There are a number of valuable books that are often sold well below their market price, and the key to making money on them is to get them when they are at their lowest. Automated price adjustment programs often create a situation of one computer competing against another computer for the lowest price in Amazon listings. If you watch carefully you can benefit from these and buy at a very low point indeed.
Some booksellers just don't have time to manually check the value of a given book. They receive thousands of books daily, they price them according to a system they've designed, but they are not set up to catch the odd highly valuable book because they are set up for volume. An example of these types of books is "Rage" by Richard Bachman. It can sell for up to $600 or even higher, but it is simply a normal-looking paperback that you wouldn't take a second look at unless you knew Stephen King was making an effort to get all of them off the shelf (because of school gun violence).
I have seen this book sell for as little as $5 (when I bought it) or for as much as $1,000. "Rage" is not the only example of this kind of pricing disparity. There are likely hundreds of inconspicuous looking books that are worth hundreds of dollars sitting on a shelf somewhere near you.
It is easier now for automated systems to catch these discrepancies, but they do still happen, and it is trivial to catch them when they do. Also, many booksellers are not full-time dedicated sellers and just want the stuff gone. There are also ways to force these discrepancies to happen-- computer pricing algorithms often will lower the price of these books well within range of good value.
For a large book seller, the longer they keep a book the less profitable it becomes. So they have algorithms in their pricing to make sure that they have the cheapest book at all times. Their algorithm monitors pricing of similar books and lowers their price to be the number one displayed offer on Amazon. So when two computers go to war over being the lowest price, you can purchase at the bottom if you are watching.
If you already have a copy of the book, there are times when you can create a no-lose price battle in the Amazon listings. If you have a listing, and you lower your listing to be the top offer for the book, and you see a large seller adjusting their price downward each time you change your price, you are likely dealing with a computer. If you slowly ratchet down price and watch theirs drop, you can generally buy their copy for far less than it would otherwise sell.
These books sell slowly, and usually this is not a big risk, but you have to be aware that your copy of the book might sell at a low price as well. In general, because people are not watching these books day in and day out, you will succeed and end up with two well-priced copies of a rare book instead. If there are multiple merchants lowering their prices along with yours, you can end up with more. Some of the more interesting books I have done this with are "Rage" by Richard Bachman, "Squanto" by Feenie Ziner, and "Minimum Design" by Philippe Starck. All of these books can be occasionally purchased for under $10, but sell for over $100. "Rage" in particular, I bought for $5 and sold for over $600.
A critical element to success in this area is to get the right edition. One edition of "Rage" can be worth over $500, and another edition no more than $10. But you can use this to your advantage as well. Many times someone will list the incorrect edition in the expensive listing area on Amazon, and that will often bring the valuable editions down in price far enough to make them worth buying. I would not recommend listing incorrect additions yourself to drive the price down, but if someone else is doing it there's no reason not to benefit from it.
Again, it is critical that you know the correct ISBN, the correct printing, and the correct year of the book in question in order to make money on this. If you order the book and it does end up being incorrect, you need to contact the seller and either return it, or as is often the case, they will let you keep the book for free because it's not worth the shipping to return it. Over time you can build up a small library of these valuable books and keep them listed, occasionally driving down prices to buy competitors' books.
And when the one person who does want to pay $500 for a book comes along (this is not a situation where you're going to make a sale every day or a sale even every week these take months in order to bear fruit) you will be there to sell.
To reiterate, just a few of these interesting types of books are "Rage" by Richard Bachman (you want the 1977 paperback for this which is ISBN 045-107-6451) it's not much to look at I agree, but it is sought-after because Stephen King is has expressed a desire to get all these copies off the shelves of stores. "Rage" is a well-known overpriced novel though.
Philippe Starck's "Minimum Design" from 2012 is both a more impressive book and less easy to find with a good margin. the ISBN for this book is 886-6480-304 and is a hardcover edition from 2012 with a razor cut edges on the covers.
One other interesting paperback is "Squanto" by Feenie Ziner this one is interesting because there are times that the paperback edition is more valuable than the hardcover edition. I feel much more confident purchasing books like this when I know the reason for the value, but in this case there's so much variation and so many chances to buy this book cheaply and sell it for $100 or more that I have overlook it.
Unfortunately, recently the price of the hardcover of Squanto went over $1,000 and I have yet to find a cheap copy of it. But the easier softcover edition is ISBN 020-802-2740. if you know other books that are similarly odd and seemingly overvalued (so-called 'ugly ducklings') send comments to firstname.lastname@example.org.