I bought a box lot of some items (Board Games) I collect at an auction recently and in the box was another box full of D&D stuff. I gave the figures to a relative who plays the game but he wasn't interested in any of the little books. I was thinking of selling them but don't know if it is worth my trouble. It is a set of 13 different miniature Advanced Dungeons and Dragons Books. All the books are about 3.5 x 4 " & have orange spines except one, it is blue. I have been looking for info on them but everywhere I look it says sold out. Are these rare? Any idea what I should sell the set for (excellent shape, almost look new)?
Those books were licensed reprints done by a now-defunct third party company, Twenty-First Century Games, sometime in the late 1990s or early 2000s after TSR had been bought by Wizards of the Coast but before WotC began publishing their 3rd edition of D&D. They were created specifically for the collector's market, and it appears that their value has gone up since then. They are long since out of print.
Depending on the exact books and how many you have, these are worth a bit of pocket change compared to their original retail value. Noble Knight, an online retailer specialising in out-of-print roleplaying and wargaming products, has a section for Twenty-First Century Games's AD&D reprints that lists the miniature Dungeon Master's Guide at US$50, among others. Currently, eBay is listing a sale of the miniature Wilderness Survival Guide at 51 Euro (~US$64) or-best-offer (plus shipping from Italy), but that's probably not an accurate valuation of the book, as Noble Knight is selling the same for just US$15 plus shipping.
The value of your books individually is probably somewhere in there. Depending on the exact composition of the collection, it may also have additional value as a set to someone.
And therein lies the difficulty: you won't find anywhere to unload these for full value without a bit of work, and some skill in selling collector's items. The easy route would be to sell them to a reseller like Noble Knight, which will give you some fraction of their value but is relatively effortless; the hard route would be eBaying them or similar, as a set or individually, but only you can factor how much your time and the headache of shipping is worth to you.
I don't think this has given you a full, stand-alone answer that you can skip off to the bank with; but I hope it has given you the means and knowledge to move forward in the direction that most suits your resources and goals.