This is the fourth book in a very naff little series which is very VERY much in the classic sci-fi niche.
The author, Bulmer had a lot of pseudonym's which he used for his formidably large writing career and Tully Zetford is the name attached to this book.
The scenario is that our uber-human hero, Ryder Hook, was part of an experimental program to produce enhanced men. He did not complete the program, but is still almost superhumanly enhanced compared to regular people. This occurs in a galaxy far in the future when human have populated heaps of different stars and systems, the space ways team with different human and alien craft and a multiverse of worlds await the explorers.
The book takes up after the #3, when Hook and two friends are traveling in a space ship attempting to escape the true 'boosted men' who may be pursuing them after their last adventure. Hook becomes separated from his friends and while trying to find them ends up on a world where everyone is hunting for this fabulously expensive substance, the 'virility drug' of the title. It is not a Gene, as far as we know by the end of the novel. No Genes were harmed in the making of this book...
It is not bad, it is very much genera and will be an ok read for people who like this very hyper-masculine heroic writing. It is really dated though, in a lot of ways and if you are not already into this style of classic sci-fi, please don't make this book or this series your gateway.
The main fascination that I have for this book is how much it resembles E. C. Tubb's Earl Dumarest saga. There is even a dedication to Dumarest in the beginning of the book! I would love to know the story behind the association of the two authors and these two incredibly parallel series.
Tully Zetford is really Ken Bulmer, whose books I collect. A great ending to this one, but the story in general was not as strong as earlier ones in this series. I still enjoyed it.