The Book of Skulls
by Robert Silverberg
Media: Mass market paperback
Cover art: (unknown)
From the Book of Skulls comes the secret of life:
"The Ninth Mystery is this: that the price of a life must always be a life. Know, O Nobly-Born, that eternities must be balanced by extinctions, and therefore we ask of thee that the ordained balance be gladly sustained. Two of thee we undertake to admit to our fold. Two must go into darkness... Is there one among thee who will relinquish eternity for his brothers of the four-sided figure...? And is there one among thee whom his comrades are prepared to sacrifice...? Let the victims choose themselves..."
Four college students journey into the desert seeking the Brotherhood of the Skull and eternal life. But whether the promise of eternal life is real, and which two must die so that the others may attain immortality, only the grinning skull among the rocks can say for sure...