Actually, I was on the brink of despairing that George has given up on the series because the most recent novel had been published almost 3 years ago in 2015. However, I have since noticed there were some similar gaps in the past.
When I saw that The Punishment She Deserves was 690 pages in length, I could both understand and forgive the long interval between publications. Despite its length, I becomes absorbed and ended up reading it quickly notwithstanding my opposing desire to linger and savour. I just couldn't help myself.
Although in any series there must be a certain unevenness in how highly one might rate any given entry, I have always found the Lynley series to be interesting and absorbing. And I have to say that this novel must just about be at the top of the list. It's is so well done, both in terms of the mystery itself and all of the interesting elements and layers that are woven around it.
For example: the theme of alcoholism is prominent, particularly in the first half. And I found myself switching from almost loathing the alcoholic to understanding and sympathizing with her addiction and plight. It seems to me that when a mystery novel can accomplish such an examination and level of insight, it reaches a very high level indeed.
Once again, aside from the mystery itself, various themes are explored, including ethnic and cultural differences, strong female characters who become misdirected, promiscuity and drugs (both to a secondary extent). With regards to those two strong female characters (apart from the main and recurring characters, I mean), one emerges able to correct her path while the other crumbles, which seems to be about how reality would transpire.
In my somewhat humble opinion, Elizabeth George is able to absorb the reader into her characters and their struggles and emotions better than any other mystery writer: as much as I like some of the others, such as Cleeves and Penny, for example. I feel the pain of the alcoholic, the angst of the despairing mother, the confusion of the young college student, and the frustration of the thwarted police officer with her unique personal issues.
As for the mystery itself, it is indeed mysterious and will keep the reader guessing for a long time. I highly recommend The Punishment She Deserves in particular and the whole series in general. If you haven't been following the series, I do believe that you can delve into and enjoy this novel very much on its own, so don't become dissuaded by the sheer number of volumes in the series.
As a bit of an aside or addendum, when I went back to look at the history of the series and the 30 year passage of time, I see that George has been able to keep her characters at roughly the same age despite the various life-changing events that have occurred. For example, I do not read the novel as Lynley having become nearly a senior citizen over the course of those thirty years. Nor does it seem that Barbara Havers is anything other than young middle age. With this in mind, it would seem to me that George should be able to keep the series going for quite awhile yet if that's what she chooses to do.
One other aspect in the development of the series is that Thomas Lynley's aide, Barbara Havers, has essentially become the main protagonist in the most recent novels, which keeps the series refreshing. Almost all of the secondary characters in the book are female in this tome although the male characters do also play important roles in developing the plot.