After I received my PhD, back when Lincoln was president, I read nothing but Agatha Christie for three months. Exhausting that series, I finally was ready to get back to my scholarly activities.
There are great series to be discovered on Amazon (some on Kindle Unlimited and some just cheap) and I'd like to share some of my finds with you. The first is Freeman Wills Crofts, who outsold Christie in the 30s and is a great mystery writer. His output was prodigious and his plots are great.
Sheldon Siegel has written a seven book series featuring Mark Daley and Rosie Fernandez and costarring the city of San Francisco in some great courtroom dramas.
Scott Pratt writes about a lawyer named Joe Dillard who works among the crackers and nasty judges who seem to dominate small-town Tennessee.
There are the British Mystery Crime Classics which truly vary in quality. I would download a preview of each one before putting out any cash.
A great series by Catriona King features DCI Craig. As you immerse yourself you become involved with the lives of the Murder Squad as they evolve and change with the seasons and the suspicious deaths they encounter. The series is set in Northern Ireland where the "troubles" are over but not forgotten.
My favorite series, however, is that of inspector Skelgill of England's Lake District, a man who would rather fight a pike than be a detective. He is the creation of Bruce Beckham.
You probably already know about Mark Gimenez. He writes about the Texas Hill country and is the equal of John Grisham at half the price.