Titles: The Maise Dobbs series, by Jacqueline Winspear
First time I read the book: I read book one when it was published in 2003.There are 18 books in this detective series. Masie Dobbs is the main character, who is a quiet, assertive, thoughtful, and decisive person, and is richly portrayed. The series starts post-WWI and continues until just after the end of WWII. Each plot is complex and solid.
Winspear is a wizard at weaving missing-persons cases, or murder mysteries, with historical facts and social commentary.
I do not know of any murder mystery series, even those written by Elisabeth George, that is so skillfully written.
Whenever I am feeling down, I start at the beginning again and let the elegant storytelling draw me into sunlight.