Star Maker (Sci-Fi Novel). Olaf Stapledon

A human narrator from England is transported out of his body via unexplained means. He realizes he is able to explore space and other planets. After exploring a civilization on another planet in our galaxy at a level of development similar to our own that existed millions of years ago thousands of light years from Earth (the «Other Earth») in some detail, his mind merges with that of one of its inhabitants, and as they travel together, they are joined by still more minds or group-minds. This snowballing process is paralleled by the expansion of the book's scale, describing more and more planets in less and less detail. The disembodied travelers encounter many ideas that are interesting from both science-fictional and philosophical points of view. Star Maker tackles philosophical themes such as the essence of life, of birth, decay and death, and the relationship between creation and creator. A pervading theme is that of progressive unity within and between different civilizations.