I have struggled to find a good book on IMC flying, and this is not it either! I found myself doing cartwheels in my head trying to understand Thom's stuff on ADF tracking, hold entries and so on.
Ultimately there's no substitute for getting in a plane and flying, but personally I found Richard Collin's book on instrument flying much easier to get a grasp of what I was supposed to be doing. The Thom one is more analytical, more of a straight text book, and the Collins one is American oriented.
For me the bottom line is that while Thom may be the only book which deals directly with the IMC course, it's not particularly well written, and at times makes the whole thing more complicated than it actually is.