This is not a game in its own right, but an expansion to the Mansions of Madness game.
It contains materials for three scenarios with the usual variable plot elements, a new kind of puzzle and some special mechanics just for the scenarios in this box. It also includes materials that expand the basic game and that can be used in the original scenarios - four new investigators (cards and miniatures), two new spells and extra insanity, infirmity and mythos cards, and about five extra horror counters (why not ten, since they are always in short supply once a game is really under way I ask?). There are also new combat resolution cards to expand those decks that include a new either/or test mechanism that changes the game up a little. There are also replacement cards for some that were misprinted in the original game release, and some new counters for things that should not be. Oh, and two new monsters, Byakhee and Crawling One, two examples of each, with counters, bases and miniatures just like in the basic game. There's a new kind of puzzle too, and a small number of new rooms.
The cardboard pieces are of the same high quality as in the original game, as are the miniatures.
Unfortunately the product suffers from a large number of gaffes that can only be attributed to hurried release and inadequate play-testing.
One scenario cannot be built as described by the handbook because it uses both sides of the same tile in its floorplan. A staggering number of cards are listed in the errata as misworded. Mechanics that should be interesting are actually not compelling at all, leaving the owner wondering why they were included. The new puzzle is illogical in the context of the scenarios presented. I could go on but I advise the interested reader to check out the forums at boardgamegeek.com for the details (not written by me I should hasten to add).
On the plus side, FFG seem genuinely committed to addressing the misprint issue and are offering a free replacement component package through their website ([strike]though I don't know if anyone has actually received anything but an acknowledgement letter yet[/strike] [EDIT 03/05/12] I received my replacement part kit along with a letter of apology and a complimentary novel as compensation for the inconvenience on Saturday, March 3rd[/EDIT]). The details of the corrections are also available in the errata on the website, so it's not like you can't play with what you get.
But the issues with the compelling story elements and illogical puzzles are a bit harder to live with, and I think people who infer that the play-testing audience needs to be widened for future issues are right.