In the book, Masson advocates for a completely vegan diet and provides carefully researched environmental and moral reasoning as to his position. Packed with often horrifying facts about how the animals the vast majority of the world voraciously consumes arrive on the world's plates, and how the impact of the consumption of those animals and their stolen products (milk, eggs) is one of the biggest contributors to the deterioration of the planet, The Face On Your Plate undoubtedly offers something for everyone, even the most knowledgeable about veganism.
My favorite aspect is his discussion of his path to becoming vegan and his daily life as a vegan. I was vegetarian between undergrad and law school, but certain health problems I encountered in law school caused me to ditch the vegetarian. However, my path to becoming vegan didn't truly begin until my third year of law school when I took a course that had nothing to do with animal rights or environmentalism. At the end of law school, a friend completing Jivamukti Yoga teacher training called me enraged about how humans dominate and oppress animals. Thinking of that certain course, I told her that humans also oppress other humans and that situation merits similar outrage; at that moment, I realized I could not remain outraged at the atrocities occurring between groups of humans while taking part in the pain inflicted on animals. And thus began my four month conversion period from a turkey-burger-eating law student to a vegan lawyer.
Masson also offers anecdotes about his life -- how he occasionally eats vegetarian at restaurants, how honey slips into his diet -- which, for me, proved to be the most helpful part of his book, perhaps because I already was aware of much of the factual evidence he presented. I set aside the vegan every so often for various reasons of varying merit (in my view), and I think it's important to know that even the vegan "experts" have similar experiences and tendencies.
Whether you're interested in knowing more about the treatment of animals, the effect of diet on the environment, and/or life as a vegan, I highly recommend The Face On Your Plate. You will not be disappointed.