Firstly, I must say that if, after buying this book, you are expecting to be able to hold simple conversations in Gaelic, you will be disappointed. There are several books around which will take you through graded sets of conversations - this is not one of them.
Personally, I found it far MORE useful. This, admittedly slim, volume attempts to show the absolute beginner the structure of Gaelic, and how it relates to English, to Scots, and to other Indo-European languages.
You won't be speaking Gaelic after reading it, but the standard language learning texts make a lot more sense, if you read this first. I only wiah I'd come across it BEFORE embarking on the "Teach Yourself..." version!