Kobo Canada has a new promotion up for Bestselling Mysteries & Thrillers under $4.99, good until January 19th.
There's a good batch of stuff from the Canadian branches of major publishers, which may or may not be matched at their US counterparts. Authors include Agatha Christie (2 pages of her works discounted to mostly $1.99 CAD, if you missed the 99 cent sale several years ago), Elizabeth Peters (an assortment of random titles in her Amelia Peabody, Jacqueline Kirby, and Vicky Bliss series), Martin Walker (an omnibus edition of #1-4 in his Bruno, Chief of Police series is just $9.99, down from around twice that regularly; ETA: it looks like the individuals of #2-4 are $2.99, and #1 is 99 cents and was a
freebie several years ago, so if you already have that or prefer non-bundled versions, it may work better to buy them solo), and more.
Dedicated promo page with categories:
Fascinating Female Sleuths,
Must Read British Crime & Mystery,
The World's Bestselling Novelist of All Time: Agatha Christie,
Call 911: Police Procedurals,
Spine-tingling Mysteries,
Bestselling & Popular Thrillers
ETA: Apparently, some of these are redeemable for points. But at these low price-points, I'd mostly advise spending the money and hoarding the points towards something more expensive. IIRC it's 2400 points for a book up to the $2.99 mark, and then 2800 points for a book up to $4.99 CAD in English (points are worth more for the few French-language books they're applicable to).