I am absolutely biased for this title.
It is one of the less sold titles and the setting may be uninteresting to some.

But it's the theme, setting and era of London along with the Steampunk'ish look, long coats and Arkham combat style that made me fall in love with this game.

The idea of also switching between two characters was also interesting.

The DLC's were also good especially with Jack The Ripper.

But it's not as great as the other titles but I will say that this one is Underrated for me.