As was suggested below (by Koland and Bookratt, if my memory serves me right), I am starting a thread just for mystery and detective stories offered at free or at bargain price during Read an Ebook Week.
Connie Shelton,
Deadly Gamble: The First Charlie Parker Mystery (code RE100 for free copy). Further volumes in his series, which I haven't read, were free for Kindle recently, so it's nice to be able to add the first volume to the collection (not a romance, really, but I'm too lazy to start a mystery thread right now).
Revised to add: Connie Shelton also offers
Sweet Masterpiece, the first volume in her Samantha Sweet series, for free. The
second and
third Charlie Parker mysteries are available at 50% off, as is the
second Samantha Sweet book.