There is a very serious and obvious "disconnect" in the book. It goes for quite a ways as very good and rational science fiction, and then suddenly swerves over into the Land of Oz and Dante's Inferno.
I am not at all surprised that Heinlein may have had a stroke while in the middle of writing this book. It certainly reads as though something serious had suddenly happened to the author. I think the book was only published on the strength of Heinlein's past work, and it should have been put in file 13 by the editor.