Broadchurch - Chris Chibnall, Erin Kelly
It's difficult for me to get the proper perspective on this one.  I've watched the series this novel is based on multiple times, I watched all of the FOX adaptation, Gracepoint, I've thought and talked about the events surrounding the death of Danny Latimer (or Solano) more than people should.  Which makes me either the ideal reader for this, or the worst.  I'm not sure.  Honestly,  when this book came out, I was intrigued, but not that compelled to give it a shot until I read that hints for the second series would be included.  
I've got a few ideas what those hints might be, but really, there's not much here that wasn't on the screen (which is as it should be).  Still, it was a good use of time, I thought.  
The advantage of Kelly's novel over the series is in the details, the little things she can point out that the viewer might miss, or that the camera couldn't show.  We see the Ellie's blowup about Hardy's ubiquitous lists building up.  There's breathing room for small, quiet moments like those early on between Rev. Coates and Danny's grandmother.  You can tell there's a relationship between them in the show, but we get to see some of it here, which is nice.
Kelly nails -- absolutely nails -- the relationships between the characters, in all the nuances, all the humanity these characters were imbued with.  The loves, the friendship, the banter, the . . . distrust, the antipathy, the suspicion . .. all of it. 
The biggest things the novel has going for it is that we get a get a better sense of the effect this death has on the community.  We're told that it is in the show, but here we're told, but we also see it in ways beyond Becca's inn being too vacant.
Kelly does make a few tweaks -- notably when things happen, honestly, the timeline  makes a bit more sense to me -- and is definitely clearer, we get a much better sense how long things go along.  One change is that Chloe (the sister) isn't in school when she takes off and goes to hang out with her boyfriend (it seemed to early for her to be in school, but a good way to demonstrate her trying to get back to normal life).  Anyway, the changes she made were small -- almost unnoticeable -- and entirely forgivable (when they weren't improvements).
Kelly gives almost no physical descriptions of anything or anyone.  I wouldn't know what Rev. Paul Coates looked like if I didn't know what Arthur Darvill looked like.  You get a tidbit or two about Hardy's height, Tom Miller and Danny Latimer's hair (and Joe Miller and Nige Carter's lack of it), Becca Fisher's looks.  But on the whole, there's practically no physical description of the characters.  Which is fairly annoying -- especially for those who read the book while skipping the series, I'd think.
At the end of the day, this is a gripping story about the first murder in a small town's living memory and what happens to everyone it touches.  There's hope, there's despair (lots of it), there's love, there's  . . . eh, I said it before, I'll just say it again: humanity.
Watch it, read it -- do both.  This is a heckuva story.