This book I see as supplemental to a gaelic course and/or other gaelic books, but is the book I turn to first when I need clarification or better understanding.
Its not for everyone. If you don't want to understand tenses or want to learn by repitition rather than thinking, you may not get much out of it.
If you want to understand how verbs change from tense to tense and have examples of when/how to use a tense, this will help. But it also gives much more.
I often refer to the appendices which have a good explanation of lenition, a table of prepositional pronouns (aig means at but depending on context you would use agam - at me - or aice - at her - etc) and more.
In summary, great for anyone looking for something a little more logic based than the usual learn gaelic books.