I have just finished reading the 12 book DI Nikki Galena series by Joy Ellis. I actually read the first two a couple of years ago but have completed the rest of the series during the lockdown.
These are fast-moving crime stories sent in the Fens (an area I know well having been brought up in East Anglia), each is quite different but all feature the same core team of detectives working under Galena. There are certainly enough killings to make the fictional town of Greenborough a pretty dangerous place to be.
I've enjoyed these a lot, not only are the plots reasonably complex but there is often a second 'story' going on in the background, the actual question of 'whodunnit' is not normally 100% clear until close to the end. The length of the series also allows the central characters to be built in more detail over time although each book still makes sense as a standalone story.
If you like crime books these are amongst the very best and I would certainly recommend them. I'm aware the Joy Ellis has written other books too and will add these to my list of things to have a look at in the future.
Just read the latest one published a few weeks ago, 'Fear on the Fens'. A really different plot and possibly the best yet. Highly recommended.