Adventures in the Anthropocene is her record of the people and places she encountered on a huge global tour.
The book details how humans are altering the planet, but it also tells the stories of how we are learning to limit and cope with that change.
The Royal Society Winton Prize is worth Â£25,000 to the winner.
"Anthropocene" is the word used by many scientists to describe the epoch of humanity's profound influence on the Earth.
There are arguments over when our activities started to distort natural processes, but there is no doubting the effects today.
Pollution, species loss, over-exploitation of water and mineral resources, and of course climate change. The list goes on. This is "the age we made".
Gaia knew all the data from her job as a science reporter, but she wanted to see the impacts first-hand. So, she put on hold the nine-to-five existence and bought a one-way ticket to Kathmandu, to start a personal odyssey and directly sample some of the global upheaval.
She expected to be gone no more than six months, but two-and-a-half years later, she and her backpack were still travelling and still talking to people about their experiences.
Adventures in the Anthropocene is not simply a book of doom and gloom. It has many inspiring characters.
These are the individuals with bottom-up approaches to meeting the particular challenges they are facing - like the man making his own glaciers in the Indian Himalayas to store water for his neighbours, or the Belize man who has built an island habitat out of rubbish that he's collected from the sea.
"I really wanted it to be an optimistic book, because I'm an optimist; because we are incredible, we are ingenious, we are this resourceful species," she told me.
"So, yes, although we've put ourselves in this position, and are reaching all sorts of crises in various different ways in terms of food, water, energy, etc - we're also very capable of turning things around.
"I met incredible people all around the world who are already doing things for themselves.
"They're not waiting for someone in Berkeley, or Yale, or Oxford to come up with amazing solutions (although perhaps that's where the solutions will come from); they're also coming from the people who are living in conflict with our massive changes. We need to learn from them."
You can listen to Gaia talk about her book in the audio interview at the top of the page.
And still available to hear online is The Age We Made series of radio programmes that Gaia presented for the BBC World Service.
The four episodes (1, 2, 3, and 4) can also be downloaded as podcasts.
Gaia Vince blogs at Wandering Gaia
Last year's winner was a book called Stuff Matters by Mark Miodownik that explored the importance of modern materials.
The full shortlist for the 2015 prize was:
You can read sample chapters from all the books at the Royal Society website.
Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos
The UK's premier prize for science books has been won by Gaia Vince - the first female writer to claim the award outright in its near 30-year history.