Apparently, this is one of Heinlein's few attempts at fantasy. He does it quite well and it is notable for two things. Firstly, Heinlein cannot resist the need to rationalise the miraculous. Magic arises from a more advanced mathematics and science than our own. Secondly, we see this fantastic world through the eyes of a protagonist drawn from our contemporary world. He is a character we can all relate to and, through his eyes, relate to the fantastic events that transpire.
Most importantly though is that there is no simple "happy ever after". What happens after and how one makes the adjustment back to mundane existence is an important part of this story. Can one return to to normal afterwards or is is one forever changed?
There is a fair bit of Heinlein's social commentary and didacticism in places but that's only to be expected. It is at least thought provoking even if you don't agree with everything he says. He is continuing to impress me with his versatility as a writer and look forward to my bext Heinlein installment.