It is a very good book, probably the best one on shiny as there are few resources to begin with. However, it does play favourites amongst topics and some basic concepts are i think left to the reader to discover on their own. I would have liked more in terms of reactivity, tidy evaluation and security and maybe less on writing packages. Even with familiarity with listeners, i feel like shinys 'grammar of interactivity' still feels a bit alien and syntax bloated. As i dive more into the world of shiny, i am finding interesting results and the book has not maybe prepared me for troubleshooting these the way say ggplot or R books give you an intuition about what the issues are coming from. However i believe over time, it will become more intuitive or be superseeded by a different paradigm.