Ruth Galloway 1 : The Crossing Places by Elly Griffiths

Trade Paperback.  Highly recommended! The start of a great series!

The first entry in the acclaimed Ruth Galloway series follows the "captivating"* archaeologist as she investigates a child's bones found on a nearby beach, thought to be the remains of a little girl who went missing ten years before. 

Forensic archeologist Dr. Ruth Galloway is in her late thirties. She lives happily alone with her two cats in a bleak, remote area near Norfolk, land that was sacred to its Iron Age inhabitants--not quite earth, not quite sea. But her routine days of digging up bones and other ancient objects are harshly upended when a child's bones are found on a desolate beach. Detective Chief Inspector Nelson calls Galloway for help, believing they are the remains of Lucy Downey, a little girl who went missing a decade ago and whose abductor continues to taunt him with bizarre letters containing references to ritual sacrifice, Shakespeare, and the Bible. Then a second girl goes missing and Nelson receives a new letter--exactly like the ones about Lucy.

Is it the same killer? Or a copycat murderer, linked in some way to the site near Ruth's remote home?

*Louise Penny