On what does the author base his story in the nonfiction book, In the Kingdom of Ice?

This non-fiction story was based on the actual captain’s logs that George De Long kept during the three years of the Jeannette’s expedition which turned into an ordeal rife with suffering and disappointment and disillusion that ultimately led to tragedy. After the sinking of the Jeannette and the men were basically on foot, De Long left messages about their progress and status in cairns on the various islands they encountered. He was ever mindful of the historic nature of their ordeal and whether they survived or not, he wanted their story to be told.