What is the author's tone in Sailing Alone Around the World by Joshua Slocum?

Sailing Alone Around the World by Joshua Slocum has a unique tone for a memoir. Slocum is well known for being an avid and competent sailor, one who is straightforward and conscientious. Despite Slocum's expertise, the book reflects that same tone without being overpowering or biased to the point of being viewed as the work of a zealot who has devoted his entire life to virtually every aspect of the sea.