For intermediate students or anyone following a course in Portuguese, this book is fantastic. I've been having trouble finding a good grammar book for Portuguese, as my required course book explains all the grammar in Portuguese, making it difficult to thoroughly understand everything.
This book is detailed but not difficult to understand, with clear examples, instructions and parallels in English. It doesn't look very glamorous but I found it incredibly useful. The standard of grammar included ranges from simple things like articles and plurals to things which I have found impossible to pick up from the aforementioned Portuguese grammar book, like the subjunctive and the personal infinitive.
There has not been anything that I have needed which has been excluded from this book, including irregular verbs, summaries of every tense and voice that I have had to learn, and even a bit of idiomatic vocabulary.
It's not the only thing you need to learn Portuguese, but it's by far the best grammar book I've found. Great value for money.