What is the author's style in A Salty Piece of Land by Jimmy Buffett?

Buffett uses a first-personal narrative throughout A Salty Piece of Land. On occasion, he shifts from Tully as narrator to Willie Singer - continuing in the first-person - through letters written to Tully. In doing so, Buffett can keep the reader informed of what progress is being made in the search for the Fresnel lens when Tully is not directly involved.