Choose you own Adventure meets AD&D.  These were the Harlequins of the D&D world - almost everyone's picked up at least one or two of these.  After a couple, they all start sounding the same though.  Aimed at younger readers, you are usually a kid in the story, with a wooden sword and pet shmoogie, and you must run past or trick Orcs, Goblins and Trolls so you can save the world in a hundred pages.  Many were authored by Rose Estes.  They did cover a broad range of TSR worlds including D&D, Top Secret, Gamma World, Conan and a few more I can't remember probably.  As far as I know, there are 36 altogether, although the first 12 seem to be the most ubiquitous.

Then came the Super Endless Quest books, more commonly referred to as AD&D Adventure Gamebooks.  My favorite is #4, the Soulforge, outlining Raistlin's test in the Tower of High Sorcery.  All of these books were similar to the Fighting Fantasy series, using dice to cast spells and combat foes, and were significantly more exciting than the Endless Quest books.

Crimson Crystal books were similar to Endless Quest books but only four exist, and they had these cool pictures that you put a red filter over to see hidden items and such.

Haven't looked at the Fantasy Forest books yet but they appear to be Endless Quest type books for very young readers.