A Mate for Christmas is pretty much the last of the Moon Shifter books, so if you haven't read any of the Moon Shifter books stop right there. The bottom line is this is the closer, in A Mate for Christmas Katie is tying up the loose ends. Granted this is the story that pulls Nathan and Noel together, but you get a lot of pack too. If you have read a few you will be fine.
Overall, a nice holiday read for those who have loved Moon Shifter books. A nice read for those who wanted to see how each of the other couple have faired after all this time. So, if you already a fan go for A Mate For Christmas. If you haven't read any books stop and go back.