The Taxidermist is the first of the Heavy Rain Chronicles downloadable 'episodes'. It comes bundled with the special edition version of Heavy Rain (HMV exclusive in the UK, probably pre-order bonus in other countries) and is rumoured to be made available on PSN later this week.
Each Heavy Rain Chronicles episodes will examine an event relating to one of the four main characters before the event of the main game. The Taxidermist stars Madison Paige, the journalist who is investigating someone whom she suspects as the Origami Killer. Spoilers warning!
The (only) setting of the game is a shabby house not too dissimilar to Ethan's post-Joshua era. There are five total endings to be found and each can be gained depending on the actions of Madison. The first time I played Madison accidentally broke one of the taxidermist's 'collection' which alerted him when he arrived home. This ultimately led to Madison being chased around the home before being killed. Or you can have Madison be a bit less reckless or clumsy whilst investigating before making her escape when the killer returns.
Those who has played Heavy Rain and has been hoping that The Taxidermist will focus on Madison's back story (for example the origin of her insomniac condition that has been mentioned plenty of times in the main game) will be disappointed. Alas perhaps some things are always meant to be left vague but again perhaps Quantic Dream is planning more Madison related DLC. The cynical person in me believes so.
As to whether The Taxidermist is worth the price of admission, I can't answer that as Sony has yet to release pricing details. The storyline isn't all that great and does not contribute in any way to the original story. In fact all five endings can easily be obtained in about an hour or two. Still The Taxidermist gameplay felt fresh compared to the main game. The stealth approach to gaining a few of the endings is something very different to the vanilla Heavy Rain game.
Personally I believe that it is worth no more than two quid (or about US$2.99) and only if you are a fan. It just felt more like a demo. Overall, a good add-on, but a very short one.