Here's the deal: Extinction Evolution is now the fourth (out of five) books in Nicholas Sansbury Smith's Extinction Cycle series. If you've read the previous three, then you know what to expect here - vicious Variant violence, great military action, and human scientists continuing their quest for a biological weapon that will eradicate the threat decimating mankind. If you have not read the previous three, then you need to start back at the beginning with Extinction Horizon pronto.
As this is book number four and the final novel is a short ways off in the distance, Smith picks a fine time to shake up the series formula a little bit and introduce a few new wrinkles. What, exactly, the main wrinkle is can be easily discerned from the title. The Variants (think along the lines of zombies with a dash of parasite DNA weaved in, but supremely aggressive pale-skinned people eaters), already a massive threat in this apocalyptic series scenario, have upped their game and developed a few new unusual characteristics. They seem to be getting smarter, and are starting to adapt to their environments. In a cool little check-in with military bases around the world, we find out that Arctic Variants are a thing, and the nasty critters wreaking havoc in the Middle East are making like camels and growing humps to store water. These are neat bits of escalation, but Smith doesn't stop there and I won't ruin the surprises.
The main thrust of the narrative stems from a crucial point of evolution for these monsters, while the human element revolves around scientist Kate and Ghost Team operator Reed Beckham's deepening relationship as she continues to search for ways to develop and engineer the means to end the threat of the Variants once and for all. Along the way, we're introduced to a new team of military commandos dubbed Variant Hunters and headed up by a man name Garcia. Their story meshes well with that of Ghost Team's, leading up to a propulsive and firey finish.
Smith is really good at crafting suspenseful action scenes, and with Extinction Evolution he's at the top of his game. The finale is brutal in both execution and the emotions it provokes given how long we've been spending with these characters. It also ends on one heck of a maddening cliff-hanger!
From a sheer action standpoint, Smith rock and rolls with the best of them, crafting an excellent cross-genre work of military sci-fi horror. This entry might be the best book of the series thus far, but I have a gut feeling Nick's going to top himself in the finale.