I have a complete set of the 1901 Century Dictionary and Cyclopedia. It cost me $10 and I got a dozens of other books thrown in for free.
This is a great set, but I just discovered it is available on-line now at The Century Dictionary Online in DjVu
A brief search at Abebooks indicates that the set might be worth a few hundred. I love just owning it and still using it as a reference book set. The pages are in great shape the leather binding are not.
Jim
I found a pristine First Edition of **Ringworld ** at a used bookstore in Anchorage. Paid $.25 for it. Larry was impressed when I had him sign it some years later.
It’s the edition where he has the earth rotating the wrong direction. Rather embarassing for a hard-science type writer.
I found a first edition of *Charlotte’s Web * in a bright dustjacket for $40 in an antique shop. I also found a first edition, limited to 625 copies, of Gertrude Stein’s *Blood on the Dining Room Floor * in its original blue slipcase. I’m afraid to touch it.
Not a triumph but a major regret.
When I got married, my wife and I honeymooned in Scotland and Northern England. At one used bookstore in Stirling there was a mint condition, 1st edition Hobbit for only $3,000. I did not really have the cash, but I really wish I had bought it.
They now sell for roughly $20,000 and up only 15 years later and I would love to own it. 
Jim
More than that, my friend, from a top rare-book dealer, where most of the copies are these days. At least $35,000 depending how how much buzz there is about movies or potential sales of movie rights, etc…
2 that I’ve found 
Can’t touch them…and no pointing either…don’t even look at them…
An autographed Douglas Adams Dirk Gently’s Holistic Det Agency hardcover.
A beat up and tattered, but autographed, Frank Herbert Dune Messiah paperback.
So if Peter Jackson signs up to do a movie of Buck Rogers, I’ll be farting through silk?
I’m sure this doesn’t count, but our local used bookstore is AWESOME.
I told him I was looking for a copy of World War Z. He picked one up while he was in Pittsburgh, and sold it to me for $6. Brand new, doesn’t even appear to have been read.
I’ll be getting him a list of my Heinlein wants quite soon.
If I were you, I’d send him a script treatment, like, yesterday.
It’s not a collector’s item, but about ten years ago I bought a copy of Five Complete Novels by Dashiell Hammett at a yard sale for a dollar. Prett good bang for a buck.
A friend of mine is an antique dealer by trade and a London theatre buff. She bought an old dresser and in one of the drawers were five programme’s from a show called “Hulla Ballo” with five songs from Tim Rice and Andrew Lloyd Webber. That show was so bad neither of them list it on their resumes.
This doesn’t compare with some of the other finds but I was quite pleased to once find Bill Veeck and Ed Linn’s book Thirty Tons a Day which told of the ex baseball team owner’s hilarious efforts at running a New England area horse race track.
Not from a bookstore… Last year, I visited a charity resale shop on a day off. No the Salvation Army or Goodwill. It was one of the places staffed by volunteer ladies, with hours that don’t suit those of us with day jobs.
Yes, I bought some clothes. But, perusing the book section, I noticed an old copy of I, Claudius for 50 cents. So I added to the basket.
At home, I discovered the book was in poor shape–it was an older, cheaply made hardback. But it was autographed by Robert Graves. (According to his biographer, he did tour the US during the period indicated by the date he added to his partially illegible message.)
Between a couple of pages was a scrap of paper in the same handwriting: “Robert Graves, Esq, Deya, Mallorca.” The owner of the book was a lady, of course. Probably a pretty one.
Unrelated story: Years ago, I discovered a used book store in the Heights–a Houston neighborhood that his since become more upscale. I was bewildered by the riches. The GB Shaw collection in green binding. A Burton Arabian Nights collection. Prices weren’t bad–I ended up buying “Mothers & Amazon” by Helen Diner because Joseph Campbell wrote the preface. She was a witty & intelligent writer but the book isn’t part of Feminist Literature because she approved of female castration. (Trust me–the rest of the book is outstanding.)
I planned to return to the store later. But life intervened. When I eventually returned, the store had closed & all the books were gone.
It has been ages since I have posted, but I couldn’t resist this thread. I was a dealer in used and rare books from 1999-2004. What that really means is that I haunted used book stores and bought from small auction houses in the UK and resold on Ebay in the heydays of great prices. This was basically how I put myself through college. I had a ton of good finds, but it was always painful to know that I couldn’t really afford to keep anything.
My single best find was an American first of “Fellowship of the Rings” in a kind of tattered dustjacket, this was about six months before the movie came out. I bought it for $5 and sold it for just over $500. I also had an uncorrected proof of John Dunning’s first book that sold for $400 and cost me $10.
What I found out though is that if I was willing to spend money I could make a lot more. These types of finds were few and far between and it just isn’t worth the time, effort and fees to buy a book for $5 and sell it for $20. Most of my best books were bought at relative bargains and sold at a good mark up. My favorites were:
A first French edition of Justine by the Marquis De Sade. This was a heavily suppressed edition and came complete with erotic drawings of orgies and couples in heretofore thought impossible sexual positions. With one day left Ebay censored my scans of the drawings, but I bought it for just under $400 and sold it for $1,100.
A nice copy of the wonderful and very scarce “A River Runs Through It” by Norman MacLean. This was from a bookstore that had nice merchandise, but they were very old fashioned about condition and what would be a $1,000-$1,500 book was $125 because it was ex-library. Sold for $500.
Two Richard F. Burton books, my vote for the greatest and most fascinating man that ever lived, I bought from Cheffin and Grain in the UK. The first was “The Lake Regions of Central Africa”. The book was expensively rebound in a beautiful full soft red leather with the title in gilt. What was remarkable was how perfect it was. It was the most perfect book I have ever seen. You have to understand that to a collector and dealer ‘fine’ means something different than what a casual reader would think. For a book from 1860 it can have only the most minor smudges or defects. To call a book ‘very fine’ you must be certain, and be willing to put your reputation on the line. The text, plates and maps looked exactly as they did when the book was sold. You could put it in a bookstore today and it would pass inspection as brand new.
I picked it up with a very good copy of “Falconry in the Indus Valley” for just over $1,000. They sold for just under $3,000. To this day I regret selling the “Lake Regions”. If it was seen by a true collector with the opportunity to handle it, I could have gotten a better price than I did. I could also have kept it and not told my wife that one of our books was worth more than my car at the time.
I stopped doing it because the prices in Britain and on Ebay reached a parity where it became harder to find good deals. I also got a full time real job and didn’t have time to book hunt all the time. Someday I will go back to it and become more than the desultory collector that I am now.
If anyone has any questions about their books feel free to ask.
Several years ago, I used to buy copies of John Norman’s Gor novels at used paperback stores. I’d get backups for my faves like Dancer of Gor and so forth, without really thinking about it, heck, they only cost two bucks or so. But I felt kinda stupid about it, because I’m not really a collector of books, I’m a pure-D reader. Then the Goreans started collecting the books, and when I saw copies of Dancer of Gor going for $85 on Ebay, I felt a little better about it.
This one wasn’t a particular bargain - I think I paid about $7 - but a while back I picked up a book of collected essays by Arthur C. Clarke, which was signed by The Great Man himself in 2001; there was also a rather nice personalised dedication in there mourning all the children who’d been killed in Sri Lanka. I gave that one to my brother, who’s a big Clarke fan, as an unbirthday present.
In Atlanta, at a place called The Book Nook, I found a large stack (15-20 copies) of Fail Safe in paperback. Just for shits and giggles, I looked through them, and found a first print, first edition.
In San Francisco, I forget exactly where, I picked up The Dead Zone by Stephen King - just a paperback reading copy, but in good shape. Turns out that it was autographed by the author! No biggie, but I sold it for 20-30 bucks, IIRC.
Joe
At NYC’s Strand Bookstore, I paid $5 for a first edition of (drum roll please)…The Straight Dope.
I do not know if that wins the thread, but it definitely wins the most appropriate find. 
I love that bookstore, I passed by it over the Xmas break and I had to really resist wandering in and losing 2 hours.
Jim
I’ve got a handful of old books, but they all came from other people going “hey, I don’t want/need this anymore; would you like it?” when moving. These people had no clue what they were giving me; they just wanted to get rid of extra stuff. Out of the handful of old books, I found two that were noteworthy:
First Man on the Moon by H.G. Wells-- 1902 copyright edition
Heimskringla by Snorri Sturluson (Samuel Laing translation)-- 1930 first edition
The first one is a little beat up, but the binding and contents are sound. There’s even a bookplate noting some numbering of some sort that I didn’t investigate further, as I was still a wee bit groggy. The second one is in excellent condition, and has beautiful illustrated title pages.