Slan Hunter by A.E van Vogt & Kevin J. Anderson
A.E. van Vogt always intended to write a sequel to his most famous novel, the Retro-Hugo Award winning Slan. But by the time he got around to it, decades after publishing Slan, he had started to develop Alzheimer’s Disease. van Vogt’s wife, Lydia, gave her husband’s notes to Kevin J. Anderson, who wrote Slan Hunter and published it in 2007.