For readers new to The Case Files of Jeweler Richard series, Vol. 9 may be a good starting point, but it's recommended to begin with earlier volumes to fully appreciate the story and character development. The series has a strong focus on character relationships and backstories, making it beneficial to read the volumes in order.
While the standalone cases are excellent, what readers will remember about is the continuation of the "Diana" arc—Richard’s deceased mother and his estranged British family. The Case Files of Jeweler Richard Vol. 9