A bunch of titles in the Libby Sarjeant series by Lesley Cookman appear to be fairly recent Amazon US price drops (from $2.99 to $1.24) or US Kindle Countdown deals. (I only checked a selection at eReaderIQ, so a few of these might be more "permanent" prices.) There are a lot, so I'm not going to reproduce all of the blurbs here - you'll have to look for yourself.
Murder in Steeple Martin (#1) at $0.99:
http://www.amazon.com/Murder-Steeple...dp/B0088OVJTQ/
Murder at the Laurels (#2) at $1.24:
http://www.amazon.com/Murder-Laurels...dp/B0088OVKMW/
Murder in Midwinter (#3) at $1.24:
http://www.amazon.com/Murder-Midwint...dp/B008C2AK0I/
There is also a three-volume set of the first three titles, which may be more cost effective at $2.99 if you don't own any of them already:
http://www.amazon.com/Libby-Sarjeant...dp/B00T82V5V4/
Murder in Bloom (#5) at $1.24:
http://www.amazon.com/Murder-Bloom-L...dp/B008C2C524/
Murder in the Green (#6) at $1.24:
http://www.amazon.com/Murder-Green-L...dp/B008C2C4IY/
Murder Imperfect (#7) at $1.24:
http://www.amazon.com/Murder-Imperfe...dp/B008C2C790/
Murder at the Manor (#9) at $1.24:
http://www.amazon.com/Murder-Manor-L...dp/B008C2KV5W/
Murder by Magic (#10) at $1.24:
http://www.amazon.com/Murder-Magic-L...dp/B00883BFV4/
Murder in the Monastery (#11) at $1.24:
http://www.amazon.com/Murder-Monaste...dp/B00AQJY132/
Murder in the Dark (#12) at $1.24:
http://www.amazon.com/Murder-Dark-Li...dp/B00EHMXWQQ/
Murder in a Different Place (#13) at $1.24:
http://www.amazon.com/Murder-Differe...dp/B00JLJFJ4S/
Murder in the Blood (#15) is a US Kindle Countdown deal at $0.99 for about 5 more days before going up to $4.99:
http://www.amazon.com/Murder-Blood-L...dp/B00WJXX3F0/