There are a lot of mysteries on sale today (9/27) as part of the US Kindle Daily Deal:
http://www.amazon.com/gp/feature.htm...d_i=1000677541
These seem to include mostly Bloomsbury books, including some by Edmund Crispin (Gervase Fen), Ann Bridge (Julia Probyn), Margery Allingham, Gavin Lyall (more thriller than mystery IMO), Nicolas Freeling, HRF Keating, and others. Many have been on sale before.
I'm particularly fond of the Julia Probyn books, having discovered this author/series due to a previous Bloomsbury sale.