Five top books about achieving immortality

Neal Asher's latest book is Infinity Engine.

One of his top five books about achieving immortality, as shared at Tor.com:Riverworld by Philip Jose Farmer

In Philip Jose Farmer’s Riverworld we are resurrected to eternal life in new bodies on a world covered with a giant river valley. We awake on the banks of this river in perfect 25-year-old bodies, which can regenerate from just about any