Although intertwined with the first book of this ongoing series, Salby Evolution reads extremely well as a stand-alone instalment, though in all honesty, personally, I would still highly recommend reading Salby Damned first to enjoy this one to the full.
In book one the story was very much a localised one, concentrating on how the authorities would deal with a combined ecological stroke biological 'accident.' In this second instalment, the story naturally expands to the international repercussions of what could easily have escalated into the sort of zombie apocalypse only previously imagined in wild speculation.
The action switches from the UK to Russia, where characters who were central to dealing with the first Salby virus outbreak have been drafted in to help deal with a possible new outbreak.
This new chapter starts with two main storylines, one which quite seamlessly follows on from just a few months after the first book finishes, but with sufficient references to the past to bring new readers up to speed while providing a subtle recap for those who read book 1 first. As the story progresses, the original characters diverge to cover different aspects of the story i.e. determining if the virus has spread, has it changed, tracking down possible new carriers of it, as well as dealing with other parties equally interested in the Salby virus. Secondly, we have what I would regard as the main thrust of the story, an offshoot from the original outbreak but threatening a future one, initially running parallel to the original Salby virus outbreak of the first book but gradually catching up and converging with other threads of the ongoing story here.
I did think a little way into the book that perhaps the author had been slightly over-ambitious in the scope of the sequel with everything that was going on, the switching of perspectives and slightly different timelines but he skillfully drew all the different elements into a complex but extremely well-constructed story.
I was impressed by the way the author handled the varying stories and sub-plots, some featuring several characters from the first book and written from a third person point of view, consistent with the writing style of that book. In another, the reader is introduced to a couple of new characters but from the first-person perspective of leading man Simon, a stark contrast to Nathan, the leading man, and hero of the first book; Simon in comparison is a bit of an anti-hero, older, not the same sort of macho character and having many more flaws and personal demons of his own to contend with but still proving his worth nonetheless.
The switching back and forth between these different threads worked surprisingly well, especially the way in which the different timelines and stories converged in their relevance to the overall picture.
I was pleased that this sequel also paid homage to book 1 in that we were treated to a few more encounters with victims of the virus i.e. the 'Deadheads' - they served as a timely reminder of the surreal and terrifying consequences of the Salby outbreak - but the author didn't try to rehash them for any sort of dramatic effect but instead took the story forward, and in new directions; what started as a surprisingly intelligent and believable zombie outbreak in book 1 (but with a small 'z' I'd say), has moved slightly away from that concept and evolved instead into an equally intelligent but more complex thriller, again throwing together some of the same elements - cutting-edge bio-engineering, viral infection, and a military interest in the virus, but this time adding manevolent scientists, political ambition, and the threat of world threatening consequences - and like any good thriller, some nice twists along the way (particularly relating to Simon but some other good ones too).
Not only does this sequel expand upon the first instalment, the quality of writing itself has evolved and improved too - I gave the first book in this series a five-star rating but with the proviso that I thought it fell just short of that at maybe a 4.7 to 4.8 on account of a slight over-emphasis on military terminology that might slightly confuse a non-military reader. In this book though I think the author has got the balance exactly right.
A first-rate book both in its own right and as a sequel, and indeed as a prequel to some as yet unknown conclusion, a very easy and solid five stars for me!