I think for me it is best to read the book first, then see the tv series or movie. This way, having seen the series first, I am always saying to myself, "Oh, that's why that happened," or, "oh, that made what happened less shocking." But I am also enjoying everything that wasn't in the series. Probably 2/3 of this book was not in the series and other parts were only hinted at. If I read the book first, then I can enjoy the production while criticizing acting, casting, production values, but mostly screenplay. However, I am enjoying these books very much because they are explaining and broadening my appreciation of the characters I met on the screen. Absolutely worth the read.
I am about to start reading Dead Man's Chest, another Miss Fisher's Murder Mystery. These are always fun and compact.