As might be expected based on the title, each of these investigations centers around a mansion although there is quite a bit of variety in terms of what exactly the adventure entails – these are simply five different, Scooby Doo haunted houses.
-- The Five Investigations --
Mr. Corbitt involves the PCs investigating a neighbor who has been acting somewhat unusual, only to discover there's something far more sinister going on across the street. Without giving too much away, the story definitely has a bit of a Dunwich Horror vibe to it. I like the premise of the adventure, which would work great as a one-shot at a convention and the investigation definitely has a purist Lovecraftian feel to it, although it has the potential for a pretty pulp-like ending. Two thumbs up.
The Plantation is a cross-country adventure, starting in New England and finishing up in South Carolina on an antebellum plantation. It also involves a snake cult and some proper cultists. As such it's much more a pulp-style adventure.
Crack'd & Crook'd Manse is probably my favorite premise of all of the book's content since it involves a house with a sinister past in which a very Lovecraftian horror has taken up residence. Unfortunately, there's a bit of a disconnect between the house's past and the current issue – the investigation ends of splitting the difference which lessens the impact of both (i.e., the background of the house is largely pointless. Overall though it's a cool idea and there's a lot of potential for a creative Keeper to mine here. This is probably the most purist-style adventure in the book.
The Sanatorium is another interesting twist on the typical “bad things happening at the Sanatorium” adventure premise since it's set on an isolated island and involves a sanatorium catering to the rich. Obviously things go wrong fast and the PCs find themselves in a Mythos experiment run amok. This is a decent enough adventure, which walks the line between purist and pulp-style play. That said, I think it would have been more interesting to make the setting a vacation resort rather than the cliché sanatorium because it would have made the whole thing a lot creepier and would be an interesting way to involve the PCs (i.e., they're all on vacation when things go nuts).
Mansion of Madness is another solid investigation with a good set-up: the PCs visit the house of a wealthy art collector while investigating a missing Boston businessman. In the process they discover that the painting within the house are far more than they seem and that multiple factions are working behind the scenes to carry out their nefarious plans. I like this investigation because it involves multiple villains, who at times are at odds in terms of their priorities, and makes good use of the 1920s setting including gangsters, flappers, and a bunch of cool locations. This is perhaps the most complex investigation in the book (due to the multiple locations) but it's also one of the most rewarding since it involves a lot of different scene possibilities ranging from social conflicts to bare knuckle brawls. Good stuff.
-- The Verdict --
Mansions of Madness is a great supplement/adventure collection for Call of Cthulhu. Best yet for me, all of the content is easily converted to Trail of Cthulhu and I've already set about creating several convention scenarios based on the adventures it contains. As such, it's definitely worth checking out.