Well . . .
If you have read all of the Kate Shackleton novels, eagerly look forward to the next one and are an all around Kate fan, you will probably want to read this because that is what we of that ilk do. . .
Anyone else? Don't bother. Read the novels instead. Then, if you are so inclined, you can read this.
The first thing I ask of a mystery novel or novella is that it be well plotted around a well constructed mystery. Did this meet that threshold criterion? Well, it isn't exactly badly plotted. It is more like it isn't plotted at all. And the mystery isn't badly constructed. It isn't constructed at all. There is no mystery.
There is a narrative of things that happened, of course, but there is no dramatic tension, no mystery, no suspense, no excitement, no anything, really, that turns a narrative of events into a plot. It's more like a vignette than a novella. "Here is a slice of our heroine's career which kind of explains how she got into the detective trade in the first place."
One can imagine Ms. Brody's editor and agent getting together over a drink and one of them saying "Frances's Shackleton novels have sold real well and she has a solid fan base but she went on vacation and it's going to be a while till she has another novel ready. What can we do to keep the readers hooked."
The other responds "I know-- let's have her put together a little piece showing how Kate found her calling. She is a good enough writer she can do that in a weekend!" And thus this little whatever it is was born.
All that being said, it is not an unpleasant or boring read. It just isn't a mystery or a novella or very satisfying to a fan who was expecting something in the same nature as the novels, but shorter. And it is, after all, plainly being marketed as a mystery.