This is a shame, because GHDM, like Tegel, tries to do a number of unique things while toying with the limits of cliche. Some heavy spoilers follow, so caveat lusor.
|Every adventurer needs some stinkin' torches.|
The maps are big, and sparse, lots of long corridors and huge chambers and dead ends. Refreshingly, the levels are mostly not stacked on top of each other but go onward and down, although some of the connections between level maps are not very clear.
The descriptions of the shallow levels are even sparser, with lots of empty rooms distinguished only by some pieces of abandoned equipment. This may seem like a rip-off until you realize that once every ten game minutes on level 1 you have a 4 in 6 chance of a random encounter, less frequent as you go deeper. And a lot of these random encounters are going to be with rival parties, each one with a motive and most at cross-purposes to each other.
There are assassins looking to kill the remaining dwarves, disgruntled human employees of the dwarves who were cut out of the treasure find, parties motivated by acquisitiveness and psychopathy, and of course up to eight groups of dwarves looking to get back what's theirs. The early dungeon is sparsely keyed because the adventure will evolve out of these encounters, until the set-piece areas of the lower levels are reached. Tough for the DM but potentially very fun for the players.
The adventure is recommended for 50-60 total character levels, a group that would easily outgun each of the rival parties and most of the early encounters, but would be more closely challenged by the lower levels. This means that the adventure can easily adjust itself for parties closer to 5th level than 10th, with the possibility of joining forces with another group as balance. Indeed, time pressure might tax even a strong party with attrition, as a good DM will punish 15-minute-day adventurers with increasing chances that a rival has already killed the monster and taken the treasure. As so often happens in the old school, this play tip is left implicit rather than stated outright.
|That's Andre the Giant there.|
Less charmingly, but equally of the period, sex intrudes: a prowling murderer-rapist, and a character of whom it is said, "beware of the loving overtures of the bi-sexual Sabra!" I can't imagine anything other than awkwardness coming from playing out either NPC, now or back then, but you might be different.
I'm not sure if or when I'll get to run this module, as it will probably take several sessions to do it justice. But as an object lesson in how to design a complex social dungeon, beyond the stock answer of "rival humanoid factions," it's very useful.