Soho Crime currently has a number of $1.99 specials on standalone and 1st-in-series novels, which are couponable @ Kobo. As is usual for Soho, these are generally quality works, some from award-winners and nominees, from various countries, including Sweden's Helene Tursten (whose series has been adapted into a long-running and highly popular set of TV movies). A couple of them have been previously offered free or deep-discounted in various stores, so you might need to check your libraries before purchasing.
I'm doing last minute shopping before my coupons expire, so h
ere's the auto-search linkage, which should pull all of them up.