There are two versions of it:
The Apothecary Diaries The first comic is very mystery-oriented and is what convinced people to try making an anime. It is full-on Sherlock Holmes/Dr. House. This is the one I read.
The Apothecary Diaries: Maomao's Notes from the Inner Palace The second comic follows the same story but is way more faithful to the novel, so they have a lot more romance than the version I read. It's got that shoujo appeal, making it more like Grey's Anatomy.
EDIT: as for why I like it. Lots of schemes.