Keep in mind that this book is not the place to start if you haven't studied Irish before (or studied other languages from a grammar-intensive perspective). If you are just starting, save this for later and get a basic course that includes audio (you MUST have audio with Irish). If you can find it, Irish on your Own is a good starting place, or if you're really serious, Learning Irish. With that disclaimer, here's my review:
I studied Irish some years ago fairly intensively, and I was always annoyed by the lack of a book JUST LIKE this one. I've had it only a few weeks, but have had a chance to examine it and work through some of the exercises. It is something that has been sorely needed for a long time. If you are familiar with Irish language resources, you may recognize the author's name--Nancy Stenson (she is a linguistics and Irish language professor at the University of Minnesota). She compiled a huge series of worksheets to accompany "Learning Irish" in the early 1990's (I was lucky enough to find and print them out some years ago from an internet server archive). She has now written two Irish grammar workbooks. I don't have the second yet--Intermediate Irish--but soon will.
Stenson's Basic Irish is wonderful. It covers all the basic grammar/structure concepts AND offers page after page of various types of practice problems--filling blanks, sentence manipulation, verb conjugation, sentence negation, translation both ways, correcting errors, and more... just tons of good stuff!
Here's a summary of the sections: Spelling and pronunciation, word order, lenition, mutations, nouns and articles, classes and cases, ... , prepositions, numbers, verbs I & II & III, irregular verbs I & II, copula, verbal nouns, adjectives, pronouns, and a few other topics.
As you can see, a lot of info--and it all has in-depth explanation and tons of practice problems. This is a lot like the types of grammar workbooks that are available for all of the major languages. With some of the latest Irish learning materials available, there is now a pretty rich pool of resources out there and this book, especially, fills a huge void that has been there for years.