First of all, my view of Andreas Wagner is that of an uncompromising scientist, who has dared to attack some of the most difficult, intriguing questions in biological research. I 've heard him talk twice, once in Barcelona while I was a post-doc and once again in Athens while still a post-doc, only a better-experienced one. Both talks were inspiring, to say the least (not very common for scientific talks, at least for me) as was my reading of his book "Evolvability and Robustness in Living Systems" which soon followed. At the core of Wagner's research lies a very important question: "How does innovation arise in living systems and how is it compromised with the ability of all organisms to survive in ever-changing conditions?". It so turns out that the two need not be compromised, instead one is actually a prerequisite for the other. The same ability to constantly innovate is paramount for the survival for every known organism but, more importantly, it is the necessity for adaptation in changing environments that calls upon the creation and conservation of mechanisms that drive innovation. This last realization is at the same time revolutionary and extremely important and research in Andreas Wagner's lab has been pivotal in our understanding of it.
"Arrival of the fittest" is taken from a phrase attributed to Hugo de Vries, according to whom "Natural [by the time Darwinian] selection may account for the survival of the fittest. Not the arrival of the fittest". Wagner is thus keen to remind us that the early seeds of the above-stated question(s) have been planted well before the advent of molecular biology and the flurry of genes and genomes. To put it more plainly (and prosaically), Wagner uses the example of the arctic cod who has come up with an antifreeze protein that allows it to survive extremely cold water habitats. The question that arises is how was this protein "chosen" out of the superastronomical number of alternatives that could have been created with the same number of aminoacids since it would have taken many times the age of the universe to traverse the "universe" of sequences even assuming extreme mutation rates? Wagner does a great job in stating this question, explaining why it is so important (hint: it reduces Darwinian Selection to a trivial factor) and giving a good idea of the complexity that comes with it. He is also spot-on when producing an excellent metaphor that links the enormous (indeed super-astronomical) complexity of molecular structures, alternative metabolic organizations and regulatory circuits with Jorge Luis Borges' "Biblioteca de Babel" (which I, as a huge fan of the Argentinian particularly enjoyed). Wagner is at his best when describing how the mere size of this "library", its endless possibilities of alternative texts that at first sight appears to make innovation a "needle-in-a-haystack" problem, is at the same time its great power. It is in the next-to-last chapter "The hidden architecture" that, through a thorough and well-structured argumentation, Wagner shows how the complexity of biological systems, coupled with self-organization allows an extremely, totally counter-intuitive entanglement of radically different outcomes among alternative "texts", which in turn make apparently "impossible" jumps from one phenotype to another rather plausible.
Plausibility is the key word here, even though never mentioned in Wagner's (witty and modern) prose. The book attacks the same question that Marc Kirschner and John Gerhart went after in their "The plausibility of life", a highly recommendable book on what is now simply called "evo-devo". And while Kirschner and Gerhart focus on the part of development and the creation of hierarchical body plan structures, Wagner extends the concept of a hidden architecture as an all-encompassing principle in living systems. Here lies, the only (yet somehow major) flaw of the book, which is the fact that a significant part of the material is presented in the same way, in some cases in an almost identical manner, which renders the text rather dull, especially in the crucial (as any writer should know) middle part of the book. In his attempt to demonstrate the universality of the "complex library" concept (the term is mine), Wagner becomes quite repetitive and this steals a lot from the book's originality.
In total, I would highly recommend this book to the "uninitialized" outsider who would like to know more about some of the most profound problems of biology, as he/she is bound to enjoy most of it and take advantage of some of its redundancy in better grasping the main points. On the other hand, I believe that the aforementioned "Evolvability and Robustness in Living Systems" is much better suited for both biology undergraduates and postgraduates.