The James Michener novel 'Alaska' (6 letters) and 'SPACE' (5 letters) are two of his most popular works. 'Alaska' is a historical fiction novel set in the 19th century, which follows the lives of several characters as they explore the Alaskan wilderness. 'SPACE' is a science fiction novel set in the future, which follows the story of a group of astronauts as they explore the universe. Both novels have been praised for their vivid descriptions and captivating storylines.