"The Peace Negotiations: A Personal Narrative" by Robert Lansing
Robert Lansing was President Wilson's Secretary of State. He did not agree with many of Wilson's proposals and tactics and was eventually marginalized by Wilson in the negotiations team. Lansing resigned as Secretary of State in 1920. This book is a fascinating account of what happened from Lansing's perspective. Many of the differences he had with Wilson can be argued to have been right, in light of the generally accepted belief today that the negotiations were a failure on many levels.