Hat tip to "moregon" over at the www.bigfootdiscussions.net for sharing this.
I've never read it, but by almost all indications I see it's likely a solid work. At two different Amazon.com listings with more than 1 review (as there is 1 lone 2.0 star rating at another posting) it sits with a 4.5 and 5.0 star ratings, after 3 and 11 reviews respectively. The review that most caught my attention reads:
Here is the title page to begin reading the ebook for free:Since this book first appeared in the early 1960s, it has proven to be the basic text book for understanding this mystery. The reason for this is not that Sanderson includes all the eyewitness and other accounts concering mystery hominids/hominoids or that he surveys the entire planet in looking into this mystery. Sanderson's strength is that he was a biologist and brought the rigor of his dicipline with him. Sanderson not only describes the action, Sanderson tells you why these mystery creatures are found where they are found. He explains fringe areas and montane forests and their significance in a biological explanation of what is happening. In short, Sanderson's book gives this mystery a predictive value, telling the reader where creatures should be seen based on the geography and biology of where they have been seen to date. Anyone wishing to understand mystery hominds/hominoids should consider Sanderson's work essential and the fundamental work in the field. This holds true as much today as the day it first appeared.
From there you turn pages with the link all the way at the bottom-middle, which while you are on the title page states "Next: Dedication."
For anyone who might be interested in a hard copy of the book, I've put together an Amazon.com widget with the best prices I found of the many varied copies they are selling. In the widget there are 3 different printings of the paperback from 2006, 2007, and 2008, as well as 1 hardback from 2007. Same book, different covers.