This series started a bit slow for me; I didn't like the protagonist right off, so her relationship with other characters felt off kilter as a result. But by the third book the author found her groove and dropped the love triangle she was playing with, the MC got more likeable, and the books got much better.
Merry Market Murder, is, of course, a Christmas themed mystery and there is plenty of Christmas to be found throughout the story: trees, ornaments, snow, and a man who looks like Santa. From the standpoint of Christmas cheer and mood, this book suffers only for having followed Duck the Halls in my reading list order. (Really, Duck the Halls should have been saved for the 23rd of Dec.)
As I mentioned above, the author was toying with a love triangle at the beginning of the series, but it's resolved itself quickly and Becca is now in the "honeymoon" phase of her relationship with the town police chief. If you prefer your cozies have some semblance of realism when it comes to police procedure, you're probably going to be aggravated by this one; Sam plays fast and loose with the rules by involving Becca in quite a bit of the investigation. I don't mind it at all simply because one gets a bit tired of all the contortions authors often put the MC through trying to find out what the police know. Cooperation is a nice change of pace on occasion.
The murder plot was, eh, so-so. While I wasn't absolutely sure who the killer was, I had a pretty good idea. It's not screaming obvious, so I think most people are still in for a good mystery; the plot ends up being delightfully twisty and a couple of old secrets are outed.
Overall, Ms. Shelton writes a good book: solid characters, a well-done plot, tight writing. She doesn't torture her readers with info dumps, or paragraph after paragraph of introspection, internal dialog, and/or plot summations. I'd happily recommend this book for lovers of cozies or light mysteries looking for a Christmas theme. Just read it before you read Duck the Halls.