Phryne, her adopted daughters, Jane and Ruth, 'apprentice' detective, fourteen year old Tinker and various others familiar to readers of previous Phryne mysteries like her companion, Dot, her lover, Lin Chung, Dr Mac, Cec and Bert and the Butlers (who somehow maintain a calm, organised home for her at the same time) set out to use Phryne's often unconventional contacts to try to find out what is happening. At the same time, Detective Inspector John 'Jack' Robinson and Detective Constable Hugh Collins are using more conventional policing methods. Between them they bring all three mysteries to satisfying and unexpected conclusions.
While some might find Phryne somewhat over the top, for me, she is, if sometimes outrageous, enjoyable for what she is - an intelligent eccentric who has position, wealth and contacts as well as a well developed if unconventional morality allowing her unusual freedom of action. Her companion, Dot describes her as a force of nature. I think that probably sums her up neatly.
As to who would enjoy Unnatural Habits, although some of the subject matter is dark, it should appeal to those who like their crime with a light touch.
Phryne has her own website at www.phrynefisher.com.