This, of course, is a fallacy.
As Mr. Raggi says in the Author's Note, "But uninteresting is uninteresting no matter how original the topic, and interesting is interesting no matter how unoriginal the topic. Making it interesting is the difficult, but important, bit." So, The Monolith from Beyond Space and Time can be considered an adventure that reconstructs Lovecraftian tropes after the overworked squamous, tentacled, cyclopean stereotype.
The Monolith details a location that can be placed in any sandbox campaign: a forested valley ringed by mountains. All told, it probably encompasses a square mile of territory. The valley is Weird, though; depending upon the DM, it's possible that it's always been there, or that it just appeared one day. Perhaps it even has a fixed location, but the adventurers stumble into about twenty miles away from where it's located on the map. People who enter the valley tend to never return.
That's the setup. The valley, of course, houses the titular Monolith and contains all the weirdness that the Monolith brings with it. Traversing the valley brings one directly into contact with Things Beyond, and the entire place runs on alien geometries (it's entirely possible that the valley itself is millions of miles across, and that you'll encounter yourself from the future; it's equally possible that neither of these things are true). As for the Monolith itself, well, it's entirely worth investigating, but as with most Raggi modules, you likely won't return the same as you left. If you return at all.
This module emphasizes the "unknowable alienness" of Lovecraft and de-emphasizes the "fuck 'em and let Cthulhu sort 'em out" descent of Call of Cthulhu. In that respect, it reads as though it's as challenging to run as it is to play, as one has to explain things that don't make sense as we understand them. For example, assume there are two characters; there is a possible effect whereby one character might move, one character might remain in place, but both characters remain together. As Mr. Raggi says, "Good luck describing that to your players!"
I'd recommend The Monolith from Beyond Space and Time if you want a dungeon crawl with minimal focus on combat, or if you want to give your players a strange and unnerving experience. Or if you just want to mess with the players. If you want something more straightforward, you might want to shy away from this one.