I own four Advanced Dungeons & Dragons hardback books from the late-70s and early-80s. A search of the ISBNs gives a wide range of selling price, but was hoping to get a better idea here. These books are near-mint, don't ever seem to be opened or used, and the Deities book even has the original receipt.

Deities & Demigods: https://imgur.com/ImiIn5k | https://imgur.com/1IurV5D

Players Handbook: https://imgur.com/Y8NxnKC | https://imgur.com/4LEKAGI

Dungeon Masters Guide: https://imgur.com/USx9TMq | https://imgur.com/C0SsP4b

Monster Manual: https://imgur.com/TWxNTtj | https://imgur.com/weQCXxF

Any information on these would be great.

Thanks for your help, Allan. I've put all I think you need (and maybe a bit more than you need) here: https://imgur.com/a/PSgOow2

Let me know if you need anything else.

dbartman wrote in Old AD&D Books Appraisal:
See the valuations here:

Rulebooks Index

They are based on actual sales prices, but based on historical data to smooth out any any short-term price fluctuations.

You would be looking at the NM valuations.

The valuations on this site especially help with relative values.  When it comes to what you actually sell them for, I'd recommend starting with a higher price than what you see on this site, especially if you are in no hurry to sell.  It's even possible that someone will pay double what you see on this site for these books.  While eBay is arguably the best-known selling site, more and more people are selling through Facebook groups.  The main advantage is that you don't get gouged by eBay selling fees, but the disadvantage is that you don't have nearly as big a pool of potential buyers.  And as clean as those books are, you may just get some offers from folks here.