If you're interested in Reality Therapy/Choice Theory, I'd recommend books by Robert Wubbolding. Glasser is the innovator, of course, but he's also the "evangelist" and he tends to err on the side of generalizations and oversimplification for the sake of reaching the biggest possible audience. Wubbolding, on the other hand, really puts the arguments across in the best possible way (in my opinion).

Glasser tries to have it both ways sometimes, and his arguments can get sloppy. For example, he often says something along the lines of, "There's no such thing as mental illness", but then, if something is discovered to be the result of a phsyical problem, he says that it wasn't really a mental illness to begin with, but a physical illness with mental symptoms.

When it comes to figuring out why these things happen, though, it's all pretty complicated. Just because something shows up in a brain scan or can be treated with medications does not mean that it was caused by some kind of physical problem to begin with. Likewise, just becase something can't be measured or treated in those ways does not mean that it doesn't have some kind of physical cause.

I think that when Glasser says there's no such thing as mental illness, what he's trying to get across is that the nice medical-model idea that's been promoted by psychiatrists (i.e. the idea that mental illnesses are really medical illnesses with clearly identifiable physical causes) is false. That's true as far as it goes, but the way he puts it often leaves people with the impression that they're somehow choosing to be miserable and screwing up their lives on purpose.