A slim book. The take-away I was most impressed with is the statement that short periods of standing, interspersed with sitting or reclining were most important to readapt to normal 'gravity' fitness after an extended period of weightlessness, forced bed rest in convalescence, or continuous sitting, 32 periods of standing for as little as 2 minutes at a time each day, more effective than continuous exercise or standing for an hour at time 3 to 5 times per week. Very interesting contrast to the conventional wisdom.
But I would have liked to see some rigor, show me the data, talk about mechanisms. I would have preferred that the book err on the side of a more technical approach, this was too simplified! The portion of the book that stepped away from the NASA research with which the author was involved seemed like a compendium of related materials gleaned from the popular press.