Underrated D&D supplements

[Trask]

D&D has had so many adventures and settings that it can be easy for some to slip into obscurity, but some of them really deserve to be better known. I recently bought and read the original World of Greyhawk box set on a whim, I had only ever played the setting as a vague backdrop in some 3.5 games and never thought much of it. But after reading this, I feel like its a great example of how to do writeup for a campaign setting. Its not long, but very full of adventuring potential and intrigue between states, interesting characters, and evocative history that is kept to an appreciable briefness. It is somewhat "generic" but it makes up for that by being exceedingly gameable in a way that many setting supplements I've read just aren't. Its inspired me somewhat to maybe revisit that world. And yet despite these virtues, Greyhawk, when ever mentioned at all, is pretty much all about the post-Greyhawk wars which IMO does away with a lot of these good points.

What D&D products do you think don't get the attention they deserve?

[KorvinStarmast]

What D&D products do you think don't get the attention they deserve?

City State of the Invincible Overlord. A Judges Guild product that provides a great Urban based setting. (I am not sure if there is a 5e port of it, but I'll look around and grab it)

I am still waiting for my 5e version of Tegel manor, which is a related product, but that kickstarter went sour.

[GentlemanVoodoo]

The Maztica and Hollow World adventure sets. Nicely written adventures that offer a more unusual flavor.