'Chthon' was Piers Anthony's first novel. There is no hint of Xanth in this book, no preponderance of puns. Word on the net is this book took Piers 7 years to write, some of those years while he was in the army. 'Chtnon' has a dark oppressive feel about it at times. Hell, the title itself refers an underground, 'inescapable' prison.
The book begins with our protagonist Aton 5 entering Chthon as a prisoner. Interesting name our protagonist has. Aton (or Aten) was the sun god that the Egyptian pharaoh Amenhotep (aka Akhenaten) tried to set up as Egypt as the center of a monotheist religion. So at the beginning of the book we have a sun god thrown into the darkest underground with no hope of escape. This theme appears in classical mythology with Ra's chariot traversing the underground every night. I always saw a correspondence as well with Christ's apochyphal travels through Hell in between Good Friday and Easter resurrection. Seen in that light, the book starts to take on the stance of a more personal struggle by the author, Mr Anthony (Aton?) determined to cross the Abyss and free himself. A 7 year journey to break out and become the author he wanted to be.
There is a second plot/theme in this book. Aton 5 as a child met a siren, a 'minionette' named Malice. The unfolding folklore is interesting, everyone has a vision of an idealized love interest created as from childhood. Then about three quarters of the way through this second plot takes on a dimension that can easily be confused with misogyny. I don't think it is. Frankly it seems to me that Piers had seen many abused women in his life, maybe raised by one or early formative dating, and projects that onto female characters. Or he goes the other route and shares with us an internalized idyllic fantasy. Not misogynist merely unenlightened. Keep in mind that this is Piers' first novel and he went on to change and grow. I'd recommend his Incarnations of Immortality series to a difference 15 years later.