It's alright.
MoM is trying to address a challenging task of presenting a story-driven horror adventure with a bunch of fixed cardboard pieces. The stories are fairly well written and tight to play, but obviously after five attempts of the same scenario it's hard for players to feign surprise or horror. As could be expected (especially for FFG), this is being solved with an endless stream of mini- and maxi-expansions. Billions of fan-made adventures probably exist as well. If you only play every now and then, it's possible to have enough fresh material without repetition. If you're going to grind it every night, it's going to get repetitive.
As usual, mythos games have a high risk of converging into "yawn,
another eldritch monster...how many sticks of dynamite do I need this time?" The mood depends greatly on players. It's next to impossible to generate an endless stream of good, interactive horror stories using fixed components. For plain grinding, you may want some euro game with wooden cubes. For true adventures, you may want to run a RPG campaign.
Some mechanics such as lock puzzles are debatable. You'll notice that for some reason, every old mansion is bound to contain at least one runic puzzle lock...
Apparently the latest big expansion was poorly tested and consequently in some parts unplayable. Get a second pressing or the online corrections
before you start.
But you do get a box full of high quality room tiles, plausible plastic minis and other stuff. You can probably find a bargain somewhere, making it fairly cheap considering the large pile of components included. I found MoM quite well done. The most dubious part is the concept itself, which isn't easy to realise with any boardgame mechanics or components.
(Also see the "related topics" box that should appear below...
)