Helm presents Calvin's ideas in a way that is clear and engaging, I especially enjoyed the chapters on free-will and the extra Calvinisticum, from which I learned a lot. The book does a good job dispelling common misconceptions about Calvin's thought, such as that he totally rejected natural theology or affirmed divine command theory.
The last chapter of the book was definitely the worst, and the reason why I'm giving only three stars, for Helm projects back onto Calvin a view of eternal justification which I think he pretty obviously didn't hold. It's a shame since other than that it was a great book.
I'd recommend the book to anyone interested in Calvin and the chapters on Free Will and the Extra Calvinisticum to everyone, since they're based and true-pilled.