It's been said somewhere that Mummy's Mask was planned out as three two-volume arcs rather than six individual adventures, for pacing purposes, but my opinion and that of my group is that somehow things didn't go according to plan.
This volume picks up after the player characters clear out a tomb and are in pursuit of a cult that's taken something. But there's no trail to follow, there is merely the second half of a desert hexcrawl that began in the previous module, and the only clue is that the cultists are hiding out in the northern half of the hexgrid page in the Player's Guide.
And running that hexcrawl as written, with the group checking each space, figuring out search patterns, just kills the momentum dead. Even if you're not running random encounters, the adventure is less about the chase and more about tediously filling in the map until you find something interesting. And while there are a couple of potentially interesting encounters to be had, roleplaying and otherwise, they're all predicated on your group choosing a path that finds them. As written there are no hints, no trails, nothing to break up the monotony.
And this becomes a problem, because without some of those roleplaying encounters the dungeon just becomes a series of rooms filled with enemies. The dungeon that makes up the last third of the volume is massive -- the map of the main level takes up almost a whole page of the volume at "1 square = 10 feet" scale (which means it won't fit on any reasonably-sized mat, and you're going to have to redraw at least a few rooms because halfway through you realized you screwed up the scale). There are two different factions jockeying for position within that dungeon, but unless you took the 'right' path and found certain encounters in the desert, there's no context for one of the factions. There's just, inexplicably, another group of cultists who don't like the other one. One encounter, unless the group would have the context, is nonsensical as written because it assumes the characters are familiar with the NPC's associates. The only option is to ignore all that story and turn him into a more talkative 'fights until dead' cultist.
My group got halfway through the dungeon, but between the hexcrawl and dungeon fatigue they were ready to just turn all of the macguffins they have over to NPCs and walk away. My players, openly dreading the possibility that the next two volumes of the AP would be more of the same, have decided they'd rather play something else on our Pathfinder night.
The first two volumes of the AP go well together, because they get you invested in the city of Wati, and uncovering new layers of the necropolis makes for interesting exploration and keeps things fresh. The third volume, while a little all over the place in spots, at least has some flavorful mini-dungeon libraries. But unless you just happen to take the right route to find all of the interesting roleplaying encounters, this one is just bland desert and rooms full of nameless bad guys to kill. Maybe if the first half were a little more directed and linear, that would have helped keep the momentum up, but my players rapidly lost interest in continuing the adventure path.
