Charlie Garratt. Released 6th Oct 2020 by Sapere Books, it's 243 pages and available in paperback and ebook formats. It's worth noting that the ebook format has a handy interactive table of contents as well as interactive links and references throughout. I've really become enamored of ebooks with interactive formats lately. For Kindle Unlimited subscribers, this book is currently included in the KU subscription library to borrow and read for free.
I've been following the development of this series since the first book. It's such a contemplatively and gently written book - full of well rendered characters and deeply researched background. The narrative feels very real to the period (the verge of WW2). Although this is the fourth book, it would work well as a standalone, though I strongly recommend the previous books for the quality of the writing and plotting.
The descriptions of the French countryside and his life on the farm, the villagers in the nearby towns, and his interactions with his neighbors and family lend this such a warm and nostalgic period feel. It was a real pleasure to read. I believe this series will have high re-readability, strictly for the characterizations and descriptive prose. Beautifully done. I really enjoyed this one a lot. I did figure out "whodunnit" by the end and had a pretty good idea of why, but was still impressed by the subtleties of the denouement which I hadn't predicted.
The books do have some overarching plot threads - especially concerning James' extended family (a major plot element in book three was him trying to locate his uncle in France), but again, nothing that will especially spoil the plots of the previous books. I do recommend reading them in order if possible, since the writing is superlative.
One of the few series I've read lately which is consistently rated over 4 stars.