Only my opinion, but most mysteries can be read stand alone.
Many have ongoing characters but the best only have vague reference to earlier books so as not to spoil them.
I have read literally thousands of odd series books without feeling I know the ending to a previous book in series.
I love it when I can read them in order, but that generally I am thrilled to find a book by a favorite author I haven't read before even if read many after it.
For example: knowing Robert B. Parker's Spenser's romantic future doesn't detract from the pleasure of reading his first few books. In fact the first introduction of familiar characters kind of fills in the blank.