Well, skimming through it, it does seem nice, but I rarely find materials that don't have problems with them. For example, it does provide a lot of reassurance. In the "Assessment Tools for ROCD" section the author explains a lot of concepts they shouldn't bother explaining. When you have ROCD, you don't need to learn about your relationship or your views on relationships, you have to stop doing those things. A therapist explaining the concept of love once to you in the very beginning of therapy is not such a bad thing, as some people may need to hear it once, but a book that you read over and over again should never do this.

Secondly, they seem to be of the type that believe OCD is mostly about irrational fears, and although this may trigger many people for me to say, OCD has nothing to do with irrational fears. Your fears could be rational or irrational, the point is, it doesn't matter. Take a look at the below and decide for yourself. They sort of suggest your fears could be rational, then back away from it, so who knows.

As with any OCD issue, the truth is that your worst fears could be true but obviously are not. Probably— that is, it cannot be proven with 100 percent certainty that your fears are basic nonsense, but the evidence supporting their being nonsense is readily available.

The kind of therapy that I recommend is never, ever getting involved with your obsessions, and so far from what I'm reading they are doing a lot of that.