221B has a great range of mini-games and professional shine (it should do considering how much Warner Bros. must have spent on it) with everything from video chapter introductions and photoshop-ed 'documents' to top-down chase scenes and crime-scene Photosynths through real-English witness questioning.
The game appears to be (not having seen the film) a fully fledged prequel story to the events of the film, with the brilliant duo investigating the growing numbers of deaths of London socialite girls and the strange and mysterious events which are connected with them. It is fairly standard stuff but well told through a multitude of lettes, telegrams, newspapers and specially recorded videos.
With each new conundrum is a new chapter to be solved, filling in the blanks to the effect of 'I have deduced that the girl [was killed / committed suicide] because [she was depressed / the killed needed her jewels / see witnessed a crime]'. To even get the potential answers you must find clues, complete puzzles or coerce witnesses to reveal what they know. And THEN both Holmes and Watson must agree upon their deductions before they can progress.
You need a Facebook account to play, and to allow the site to connect with Facebook. Then it is simply a matter of answering a few 'do you prefer' questions and choosing or allowing the game to choose whether you play the role of Sherlock Holmes or Dr. James Watson. Alternatively you can elect to play both parts yourself.
The two experiences are have a different emphasis with Holme's puzzles focusing on logic and exploring environments and Watson running down or questioning suspects and witnesses. In order to get all the clues and solves the chapter, both investigators must pull their weight and communicate with one another. For example, Watson might need Holmes to suggest a line of enquiry so he can get the final clue from a witness, which leads Holmes to find a hidden document in a suspect's room.
Cleverly, the player does not technically need to solve everything themselves. Casual players, or those who get hopelessly stuck, or those who just don't enjoy a particular kind of mini-game, can exchange Reputation Points earned from completing other puzzles and successfully wagering on a correct deduction to automatically succeed on a given task. But the highest Reputation (essentially score) and the player's own sense of self-respect can only be earned by your own hard work and intelligence.
It is also an impressively long game - I have been leisurely playing on and off for the whole afternoon now, have reached Chapter 6 and still haven't finished. That is me playing solo. Naturally it will take longer playing with a separate Watson or Holmes as you will have to wait for the other player to find all their clues.
So 211b is a fun and varied investigative game that can be enjoyably played by both Hardcore and Casual gamers, both solo and co-op, and at one's own leisure. And it's free! What a lovely Boxing Day present. (Okay, so I took too long writing this and it's now Dec 27th... sue me).