This heavily character-driven novel begins and continues like an interesting jaunt through america in a classic road-trip novel, but it eventually becomes something much more on two fronts that might possibly be just one. 
 Is it really about joining a secret society cult based on a the Book of Skulls that promises immortality at a price? Or is it really about exploring one's sexuality, with the majority of emphasis being on homosexuality? 
 I'm not saying that being a homosexual is the route to immortality in this tale. Far from it. It's incidental, but intricately linked to what the narrator is focused on within his own mind, always swirling closer and closer and closer and never quite being able to free himself through all the meditations and weird secret-society explorations because of it. 
 It can get a bit trippy, well beyond the sexuality aspects. Very '70's writing, with main focus on enlightenment and free love and using drugs to open their minds, but more than that, this is a very deep exploration of the mind and motives and reactions to so many conflicting desires. The narrator doesn't see himself as homosexual, he sees himself as bisexual, and all of it is just as muddied as his own hunt for personal enlightenment. 
 Death? Sex? Drugs? Quest? It's all part of the same novel, and it's very interesting on all those levels and also one more: Spirituality and mystery religions. Silverberg obviously has a great deal of knowledge about them and it held my attention nearly as much as the main tale. Fun stuff. 
 Other than that, it's nominally SF. It's more a tale of self-discovery during the 70's more than anything. :)