This adventure is pretty much a dungeon crawl, although neatly dressed up with a backstory which makes it easy to provide suitable introductory events to round it out into a full scenario or to weave this little jaunt into an ongoing campaign. Alternatively, the backstory could be read out as a summary if you plan on running this adventure as a one-off game.
As provided, the adventurers are standing on the threshold of the Tomb of the Overseers, ready to go in. The map is laid out clearly, a bit linear... but such is the way of tombs of this sort (just look at the archaeological record!); with good succinct descriptions and notes on what you will find in each chamber. With a couple of exceptions, all monsters encountered are just that - something with which to do combat. The exceptions are pretty constrained in what they'll do, but should at least give those characters who like to talk rather than fight some opportunity to do so.
There is a distinct tendency for this adventure to be merely a mechanical puzzle-solving, monster fighting and item collection exercise, but this fits well in this instance because of the nature of the mission that the characters have been given. However, if there is a reason why the Big Bad Evil Guy at the end is actually there, it's not stated: however, he is the reason that the characters will want to collect all the handy items scattered around the place, so it is worth scavenging them all up!
Assuming the characters do defeat him, they will be able to complete their task, and there's even a note about follow-on events, although you will have to flesh them out for yourself... potential to kick-start a whole campaign if the ideas appeal.
An interesting note is that this adventure was published very early in the life of D&D 3e, and many of the monsters given cursory descriptions here appeared in later monster books - you may wish to track them down and so flesh the monsters out a bit before you run the adventure. But there's sufficient here to run them without, especially as they are there as combat-fodder rather than true encounters.
Overall, what seems to be a basic dungeon-bash actually has a bit more to it, if you wish to make use of it within a broader context, else if a quick fight through a small dungeon is what you need to fill an evening, this will do very nicely. Worth having around, for those nights when someone's missing or nobody feels like heavy role-play and ongoing plot arcs.