Kiriti Omnibus 1 collects the early cases of Kiriti Roy, the detective created by Nihar Ranjan Gupta in the late thirties. Kiriti was one of the first major Bengali detectives, and the series ran for decades. Bengali readers who love classic mystery often work through Kiriti before or after Byomkesh.
This first omnibus is a strong place to begin, with the foundational stories and an introduction to the supporting cast.