I haven't seen the previous Sherlock Holmes movie, and I haven't read any of the books, so I didn't know what to expect, but I enjoyed it.  
It was very much an Adrian Monk feel with more focus on action and less on characters.  There was good humor, a nice setting, and a quirky and enjoyable protagonist.  All of that lets "Sherlock Holmes: A Game of Shadows" pull off mixing plot, character, and action.