My Review on Goodreads
There are many BRMS and then there is Drools. The latest released Drools version is 8.x but then this is the latest version of Drools having a book published on it.
Tech is crazy and Drools is no exception. It has changed with each major version in a big way in terms of even the names of its components in its ecosystem. While I don't don't know yet how much there is a change between v6 to 8.x, this book covers fairly well on the Drools v6 ecosystem both in breadth and depth.
I wish there are more diagrams to visually represent the component hierarchy and the Drools runtime. I'd also wish to see the different ways in which things can be organized for a given use-case in Drools to get even better hang of the concepts.