I'm going to go out on a limb and say that this is the best book on meditation I've read, and I have read a few. I will add a small proviso though. I think this was the right meditation book at the right time. I don't know if I would have appreciated it quite as much as a completely new meditator. I also can't possibly guess if this would be a useful book for someone with decades of experience under their belts. For me, a couple of years into a daily meditation practice, this was exactly the book that I needed to read.
Rob Nairn's writing is simple and straightforward. There is nothing ornate. There isn't an excess of anecdote, allegory and metaphor. Sure, he throws in a couple of stories about the Buddha, but for the most part, this is clear simple instruction.
I feel like Diamond Mind frames the actual work of meditation in a clearer way than anything I've come across before. He doesn't just tell you to sit and focus on your breath. He tells you what you should be trying (or not trying) to do with your mind while you're sitting and focusing on your breath. He also explains why he thinks you should do these things.
I also really appreciate the inclusion of a number of exercises that are very practical and easy enough to execute. I have already found value in some of them, and I plan to re-read the book more slowly, taking the time to try each of the exercises over several meditation sessions.