First off, I must once again reiterate that the narrator sounds exactly like John Nettles (Barnaby), to the point where you cannot distinguish his voice from John's on the television show.
Secondly, this is probably my favorite mystery that I have ever had in my entire life. I have read Christie, Sherlock Holmes (of course), and is definitely a contender for the top spot of favorite mystery titles, but I must say that this one is pretty well hand-in-hand with those. 
The various story threads, each one tied up satisfactorily, was very gratifying. The people I hated got what they deserved, the people I sympathized with were rewarded perfectly.
There were also subplots, such as Barnaby with the kitten, that were perfectly adorable and helped to flush out his character, wonderfully well rounded with depth and insight. 
Even Troy was not as annoying in this one, not nearly as racist, sexist, or homophobic, (though he still absolutely is and it is mentioned several times), but had been toned down a bit to my relief.
Although I knew where the plot was going, having a scene in the television show some years ago, I was surprised at how closely the book and show were. They did not particularly television show, which is nice to see.
I must also say that the narration in this, the writing and prose was absolutely top-notch. There was a razor sharp wit and reflection of humanity in it to the point where I have actually copied several of the phrases down to use in my everyday speech.
Though I did not enjoy the first few books in this series nearly as much, you also get to see mentions of characters from those novels, and there was a strange nostalgia that they are doing OK lol. 
Definitely on my favorites list I listen to it again a second time in a row.