While I am not a huge fan of the sci-fi genre, this book was intriguing and a quick read.
This is a very hard book to summarize and review, and I believe the PBS blurb about this book is highly misleading. IMO, the "race against time" to prevent the explosion is important to the development of the book; however, I view this book as belonging more in category of "social science fiction.
It is the alien life on the moon which I believe is the most striking and central theme here. It seems to me (putting myself in the authors' shoes, which we know can be quite erroneous) that the destruction of the solar system is merely a framework for Asimov to create these aliens and play with them.
The alien social structure is based upon groups of three.These aliens aren't as compact molecularly as we are - they can soften around the edges and "merge" into one unit. This melting/merging, which is not fully accomplished until later in the story, is very pleasurable to the aliens and can be seen as a version of what humans experience during sexual intimacy. As the story progresses, we have the point of view of one alien group and, in particular, one of the three members of this group.
Taking this perspective, the reader becomes more enlightened about happenings in the book as s/he reads. Because the alien through whom we are interpreting events is young, highly emotional and not very attuned to logical thought processes, the reader experiences the growth and development experienced by the alien. As the alien gains enlightenment as to her importance and role in her triad, the reader becomes more and more able to piece together the events of the book.
TGT seems to me to be derived from our culture during the 1970s. The alien characters can be seen as the embodiment of the Parent-Adult-Child roles central to Transactional Analysis, or more accurately Freud's Super-Ego, Ego and Id.
I really enjoyed this book the several times I have read it. In fact, I bought a copy for one of my children to read and she had the same favorable impression that I did.
Just remember - this is not, despite the description of the book you see above this review, hard science fiction. The science is there, but it takes a back seat to the sociopsychological aspects of the book.
Perhaps it was the abridgement, but this was just a terrible book, very out-of-character for Asimov. It begins with a interesting tri-sexual life form, but after the first section we never hear from them again. Instead, it switches to a very unsympathetic set of human characters on the moon arguing a lot and doing nothing in particular. Then it ends with a thud. I've never given a rating this low to any book.