First, the context: I purchased this book for a class on the History of Ireland. The course covers everything from pre-historic Ireland to present day, and we've used four books. So, that being said, I can safely say that there was nothing in Townshend's book that can't be found elsewhere.
The jacket purports to answer some long-standing Irish riddles, such as how the Sinn Fein movement ended up lobbying against home rule. Townshend outlines the events that brought about the change in position, to be sure; however, there is very little in the way of analysis. And what little analysis there actually is tends to be buried under flowery language or tired old cliches.
I'll recommend it if you only want to read about recent events in Ireland, to get a feel for the names, places, and key events that still hold influence today. If you want a more thorough analysis, though, my advice is to keep on searching.