Looking for a recommendation to a good book/ tutorial series on deep dive into Spring WebFlux

I am new to reactive stack in Spring and have started developing reactive apps with Webflux + Reactive mongo together with Spring 2. But I always get stuck when finding solutions for some problem using WebFlux. I followed a basic tutorial from Udemy and Refer Project Reactor’s user documentation also.
But I need a recommendation to a book or a good tutorial series which does a deep dive to Spring WebFlux.