Inferno Series by Larry Niven, Jerry Pournelle

This is the 6th Pocket printing.Cover Artist: Harry BennettAn unearthly voice hisses unholy welcome. And the late, great Allen Carpentier begins his one-way journey into the dim nether regions where flame-colored demons wield diabolically sharp pitchforks and tormented vixens reign forever in a pond of sheer ice. Here, in this land of torment and terror, he discovers the amazing truth of the ultimate adventure that lies beyond the grave... moreThis is the 6th Pocket printing.Cover Artist: Harry BennettAn unearthly voice hisses unholy welcome. And the late, great Allen Carpentier begins his one-way journey into the dim nether regions where flame-colored demons wield diabolically sharp pitchforks and tormented vixens reign forever in a pond of sheer ice. Here, in this land of torment and terror, he discovers the amazing truth of the ultimate adventure that lies beyond the grave.Frank Herbert -"The somber beauty of INFERNO brought up to the twentieth century with care and humor and with some sins Dante didn't even suspect." less

Allan Carpenter escaped from hell once but remained haunted by what he saw and endured.  He has now returned, on a mission to liberate those souls unfairly tortured and confined.  Partnering with the legendary poet and suicide, Sylvia Plath, Carpenter is a modern-day Christ who intends to harrow hell and free the damned.  But now that he's returned to this Dantesque Inferno, can he ever again leave?