A Killer Stitch by Maggie Sefton.
This is the latest in Sefton's Knitting Mysteries. Kelly Flynn has been living in Fort Collins for some months now, and has met a lot of people, but she didn't know Derek Cooper who was killed by a blow to the back of his head. Derek's ex-girlfriend is the prime suspect, and though Kelly doesn't know her either, one of Kelly's friends knows her well, and asks Kelly to prove her innocence.
I really like this series. The characters are realistic; I can actually imagine real people behaving that way. As a plus, it was the first book in this series that got me interested in knitting again.