It's quite good. It gives you a very good understanding of Hotwire dev (Turbo and Stimulus). I recommended it only for advanced Rails developers with very good knowledge of JavaScript. Also, the React chapters will be better understood if one already has React development experience. The Cypress chapter was good but the integration with Rails didn't work for me. So, I read the content but it was not possible to actually try out what the chapter suggested. The book version I read was beta 3.0 which had quite some typing and technical errors.