All ten of the titles (so far) in the Ruth Galloway series by Elly Griffiths have dropped to $1.99, matched at Kobo. I've read and enjoyed several of the titles in this series. The first title in Galloway's Magic Men series,
The Zig-Zag Girl, is also $1.99 right now.
Info and links for all of these are in this previous post:
https://www.mobileread.com/forums/sh....php?p=3766670
Finally, the post also includes links for a long-term freebie short story,
Ruth's First Christmas Tree.