Not much replayability? Why so?
Well, the way I see it is:
The main boxed set is a fixed story you follow.
Sure, there's lots of cards and different encounters can happen along the way, but it's essentially the same storyline.
So in order to keep playing the game and keep it fresh, you need to buy expansions, whether it's a full boxed set expansion such as the "Dunwich Horror" or minor (and cheaper) expansions that are smaller storylines.
I did actually replay the boxed set a few times, but the enjoyment of it went down pretty fast for me.
On top of that, if you want to play with someone else (it supports up to 4 players) , you need to buy an ADDITIONAL main boxed game, due to the way the decks are configured.
That's a BIG investment for something that doesn't even add more storyline.
Upon reflection, I don't think it's really worth it.