After "A Case for Mars", I was eager to read more of Zubrin's books on Space Exploration. I was not disappointed.
"Entering Space" starts out by explaining what the author sees as the great shortcomings of the present space exploration strategy persued by national governments, and how all the 'cost-saving' measures have only reduced program effectiveness, but not actual cost. He pleads the case for focussed efforts on the part of governments and the private sector to open up space as the next frontier - for the good of humanity, to not only forestall extinction in case of a meteor impact, but also to rekindle the 'frontier shock' situation which has in the past always catalysed an era of progress, both social and technological. And all with present-say technology.
Zubrin goes on to describe the future course of humanity once it has established itself as a spacefaring civilisation: The Moon, Mars, the outer planets... inspirational stuff indeed. And explained in plausible, understandable terms.
Finally, the last chapters are devoted to interstellar travel, and what may lie beyond. Fusion drive, antimatter engines, magsails - all technology which is possible with our present understanding of physics, and which would make humanity's colonisation of nearby stars possible.
I highly recommend this book to anyone who looks up at a Saturn V rocket and thinks "we flew to the Moon forty years ago... why aren't we doing it today?". Inspirational stuff, indeed.