Possivelmente Século de Verão por James Blish?
An accident propels the mind of the young astrophysicist John Martels to the 250th century (23,000 years into the future), or the midsummer century. It should be noted, that according to this novel the mind is a complex self aware electromagnetic field. His mind emerges in the brain-case of a future being with a very powerful mind, the so called Qvant.
Human civilization has fallen and risen again many times and both humans and birds have evolved. In the 250th century the birds have evolved into telepathic and intelligent beings who seek to exterminate their main rivals; the humans. Humans (or the human descendents) of the 250th century have great paranormal powers but are death oriented, and have not used their intelligence to develop an advanced civilization; in fact they are not even interested in organized resistance against the birds. John Martel is thrust into a fight for the continued existence of his own mind as well as a fight for the continued existence of the human race of the future, and that is without being able to use his own physical body. In an odd way this novel also succeeded to fuse the reincarnation of the human mind with the rebirth of civilizations.