(Let me start off by saying that I reserve 5 stars for books that are truly outstanding, not, like some Amazon reviewers, for any book that is just pretty good. For me, 4 stars is a VERY good rating.)
I have felt some lingering jealousy watching the videos of the rover control center at the Jet Propulsion Laboratory. I support spacecraft for a living, but somehow what I've been doing hasn't seemed quite as exciting or sexy as working with rovers on Mars (and particularly not now, with Goddard's heyday apparently in the past.)
Squyres' book both dulls and enhances the glamor. He spends some time talking about the long, hard slog he took to become Principal Investigator for a Mars mission, starting in 1989 with an effort to develop a camera to fly on a NASA Mars mission. He proposed sticking it on a mission called MESUR Pathfinder in the early 90's and was turned down. He tried again to develop a science package to go to Mars in 1998, and that was turned down. NASA expressed interest again a few years later, he resubmitted, and it was turned down again. He put a lot of work into a complex set of missions set to start going to Mars in 2001, a program that was killed when Mars Climate Orbiter and Mars Polar Lander failed in quick succession.
By 2000, though, NASA was looking for a glamorous mission to redeem its Mars reputation, and Squyres' rover seemed to fit the bill. Not only was his mission chosen, but he was asked for two of them.
The schedule ended up being brutal, having to develop a complex mission inside of three years with the unforgiving, inflexible 2003 Mars launch window looming up ahead. Squyres relates several heroic tales of people who made the impossible possible, from Randy Lindemann coming up with a way to get 32 strings of solar cells on the rover (enough to provide reasonable assurances that it would last for 90 sols) to Adam Steltzner getting the parachutes to work to Matt Wallace assembling the rover components (and verifying them) on a ludicrously tight schedule. And you get the impression that there are dozens more stories like these that Squyres either didn't know about or didn't have space to tell. (The book includes an appendix with the names of those who worked on the rovers. There are more than four thousand of them, and Squyres admits that it's almost certainly not complete.)
There are crises of confidence as the rovers go over budget, and NASA threatens to cut one of them to ensure that sufficient attention is paid to the other. There are failed tests and last-minute problems and checks and re-checks. Even once the rovers get to Mars, Spirit has a nervous breakdown (later traced to an overflowing flash memory directory) just a few days in, right when the rover team really needs to concentrate on Opportunity's approach and landing. But Spirit recovers and Opportunity makes an interplanetary hole-in-one, right in front of the bedrock that every geologist wants to see.
The remainder of the book is a day-by-day recounting of what went on during rover operations and provides a rawer version of what those of us interested in the missions have learned in a more cut-and-dried form from press conferences and press releases. We get to read as Squyres and his team of geologists gradually convince themselves that there's no reasonable explanation for the features in Opportunity's Eagle Crater outcrop other than flowing water. He relates his disappointment as Spirit arrives at Bonneville and doesn't find bedrock, facing a long, hard drive to the Columbia Hills for even a chance at doing the geology the rover came to Mars to do. On the other hand, he relates the excitement as Opportunity descends into Endurance Crater, finding layer after layer to examine.
Then the rovers go into solar conjunction, and that's where the book ends. And that's probably the main criticism people are going to have with this book: it stops too soon. Other than Pot of Gold, the first rock Spirit happened upon in the Columbia Hills, there's little about what Spirit has learned. And Opportunity continued to explore Endurance Crater, checked out its heat shield, found the first meteorite to be encountered on Mars, and is now examining the edges of the "etched terrain." So there certainly needs to be a sequel.
The only other criticism might be that this is truly a journal, almost entirely a recounting, frequently day-by-day, of what it went through to build the rovers and then operate them on Mars. There's not much stepping back and looking at the bigger picture beyond that. But for us Mars junkies, getting behind-the-scenes of rover science and operations is fascinating all by itself. If that turns you on, then this is a great book to read.