What is the author's style in Angle of Repose by Wallace Stegner?

The story is told in parts in first person. Lyman tells his story in first person so the reader sees everyone as he sees them. Susan’s letters are also in first person for these are the personal letters she wrote to her best friend detailing her life. Lyman’s novel he is writing about his grandparents is written in third person from his grandmother’s point of view. Everything in his book, is from her perspective for he knows her thoughts from her letters and papers, but can only guess his grandfather’s thoughts and feelings so projects these through his grandmother’s thoughts.