The 'Goldilocks' part of the title, as most readers will recognise, refers to the Goldilocks zone - the region around a star where a planet would be not too hot, not too cold but just right for carbon-based, water-dependent life. As Louisa Preston makes clear, this is no longer given the significance it once was, as some of the best candidates for (low level) life in our solar system are the moons of Jupiter and Saturn, which appear to have liquid water oceans under a thick ice crust. Even so, the concept is useful.
As for the water bears, they were far and above my favourite part of the book - fascinating little 8-legged creatures that can go into a dehydrated state where they can be exposed to everything space can throw at them, from extreme low temperatures to radiation - and still come back to life when rehydrated at the right temperature. They are interesting in this context both as a type of life that could in principle support transport through space to seed a new planet and also as a model of some of the more extreme ways that life could survive in habitats that we might once have thought would never support it.
Apart from the water bears, the book is at its best in is its survey of possible places life could exist and its enthusiasm for the concept of astrobiology. But there are some problems. Large chunks of the book consist of what Rutherford referred to as 'stamp collecting' - little more than listing details of the various possibilities. This comes across particularly strongly in the section on extremophiles - organisms that can exist in extreme conditions - on Earth (as a model for life elsewhere). For page after page we get lists of bacteria and other organisms that can survive in various conditions. There is also heavy repetition. So, for example, there are three separate sections talking about the possibilities for life in the water beneath the ice on the moon Europa, with big overlaps in content. This reflects a distinct lack of narrative structure to the book, which is probably why one of the most interesting questions in the subject - if life came into existence easily, why does it appear to have only done so once on Earth? - isn't covered.
I'm sure Preston knows her stuff on astrobiology, but a science writer has to have a much wider knowledge and here she has the biggest problems. Every popular science book includes the odd error, but here there are so many, it's worrying. For instance, we are given the excellent movie The Martian as an example of a movie featuring aliens. Unless a martian pops up in the corner of a frame, or you count a potato grown on Mars as an alien, this could only be the result of simply looking at the title and assuming that it does without checking.
Things get worse when we look back into history. We are told that the Ancient Greek Democritus 'realised that the Sun was just as star... in his wisdom, he understood that the planets revolved around the Sun and that Earth itself is a planet. He even theorised about exoplanets...' But he didn't. Democritus didn't have a heliocentric model - I can only assume this is a confusion with the later Aristarchus - nor did he realise all that clever astronomical stuff. He did support (but not originate) the idea of the pluralism of worlds, but this was not an astronomical theory, more like the parallel universes beloved of pulp science fiction. Worse still, we are told that Aristotle with dates given as 460-370 BC had Plato (428-327 BC) as a mentor. Plato was, indeed, Aristotle's teacher, but you don't need anything but basic logic to suspect that Aristotle wasn't 32 years older than Plato.
Sadly, it's not just the history that is suspect - physics presents some issues too. We are told that 'deuterium is an isotope of hydrogen, but holds two neutrons rather than just one in the nucleus'. Unfortunately hydrogen has no neutrons, and deuterium has just one. We are told there was no light before stars formed, which is unfortunate for the Cosmic Microwave Background, and we are told that the nuclei of two hydrogen atoms combine to make helium, which would make it rather underweight. And, yes, inevitably, we get the myth that Giordano Bruno was martyred for his idea that there were many suns with their own solar systems.
The combination of this error rate and the lack of writing style means that overall things could have been a lot better. There is plenty of interesting material in here (though how it can be described as an 'expert romp' as it is on the cover, I don't know), but the book does not do the subject justice.
Review by Brian Clegg