Robert Silverberg's The Book of Skulls has four of the most unlikeable protagonists I have ever encountered. They aren't as actively loathsome as Holden Caulfield, but it was a matter of degree.

The worst part of the novel is the casual but unrelenting misogyny. OK, the book was written in 1972, but still -- was it really that hard, even then, to show just a glimmer of recognizing women are, in point of fact, actually human? Indeed, at one point one of our main characters pats himself on the back because of his vast compassion ... by, literally, "relating" to anonymous sexual partners as "sexual objects." Wow -- what understanding!

The story involves a college student who finds and translates an ancient manuscript and, with a group of friends, travel to Arizona in search of a mythical monastery that might hold the secret of immortality. The book is equal parts science fiction and horror, with a psychological examination of the protagonists along the way.

The plot is vaguely interesting but overwhelmed by awfulness of the protagonists. Honestly, why bother?