The work by photographer Andy Howard topped the poll from among 11 shortlisted for the biennial accolade, which he also won in 2018 for his debut title, The Secret Life of the Mountain Hare.
Naturally Orkney - Coastline by Raymond Besant was runner-up and and Scottish Island Bagging: The Walkhighlands guide to the islands of Scotland by Helen Webster and Paul Webster came third.
Niall Irvine, who organised the contest for the Scottish Nature Photography Awards, said Mr Howard had “enjoyed an intimate relationship with the area since childhood, exploring its most hidden places and developing a close understanding of its wildlife.
“In the last year, books have taken us out of the limitations of lockdown and given us a view of nature we might not otherwise have seen.
"Now is a great time to celebrate that and this shortlist did just that.”
Mr Howard said: “I’m absolutely thrilled to have won this award and humbled to have won for the second time, especially considering the high standard of books on the shortlist.
“I’m privileged to do what I do for a living.
"To spend time in the company of wildlife, to photograph and then write about these encounters is a joy.
“My job is simple, to record and share the beauty of the wildlife found in Scotland.
"I’ve cherished every moment I’ve spent in the Cairngorms, photographing the rich and diverse range of wildlife from the spectacle of an osprey grabbing a trout from a lochan to spending time on the high plateau with a dozing dotterel.
"Each and every encounter is magical and will stay with me forever.”
Robert Davidson, publisher and managing director of Sandstone Press, said: “We are enormously proud of being the publishers of Andy Howard’s beautiful Secret Lives series.
"It is tremendous the first two books in what will be a trilogy have been recognised by this prestigious award.
“Andy brilliantly visualises Scotland’s wildlife and landscapes, recontextualising them for a world in which wild things grow ever more rare and precious.”