I’ll also suggest Tree of Aeons if you want a magical equivalent (guy becomes a magical tree). Both series capture the transition to non-human thinking pretty well
Another vote for Bobiverse written by Dennis E. Taylor
Synopsis
The Bobiverse is the story of Robert “Bob” Johansson, who, after becoming financially independent by selling his software company, decides to spend some of his money by contracting to have his head cryonically frozen by CryoEterna Inc. upon his death. The idea is that his head would be preserved until later, when technology permitted a body to be grown and his thawed head attached to it - thus resuming life. The next day he is unexpectedly killed in an automobile accident. He wakes up 117 years later to find that he has been harvested from his frozen head and installed as simulation in a computer matrix to be an artificial intelligence. The series follows Bob as he is installed into the first Von Neumann Probe, to explore and replicate across the galaxy.