This is a rare combination of philosophy (verb) and also it is a philosophy. It contains a unique and insightful history of philosophy, which I thought was the best part. I have found it useful and it has contributed to my ability to analyze real world problems. I read it to help understand A Rhetoric of Motives, which I am reading now, is excellent, and which is only increasing my appreciation for A Grammar of Motives.
The only drawback, if you can even call it that, is the writer's use of Freud, which is at least somewhat tempered by skepticism, and seems to recede in the Rhetoric. He is further very informed by a Marxist philosophy, though not himself a Marxist. Again, it somewhat dates the work. That is not necessarily a bad thing, but is suspiciously ideological or metaphysically biased, or maybe its just curious.