This is me since yesterday and a few moments ago. 
 First of all, this is a very violent and most graphic book on sexual abuse ever written under the guise of PNR. If you're expecting a light reading (are you kidding me, look at the SIZE of this book) and who seem to think any kind of sexual violence satisfy your need for romantic escapism, this book is 100% wrong for you. 
 Second, Sherrilyn Kenyon was a victim of child abuse and she's been actively advocating against childhood violence (through her adult series and young adult series) and so far all of her book doesn't stray away from the theme in fact almost all of her male characters had suffered abuse of every kind and personally her writings are her way to cope with her own inner demons. If you expecting this book to fit with your "50 Shades-like romanticized abusive smut" reads, gosh, you're in for an enlightment. 
 Styxx is simply Acheron 2.0 and it never stray far from that. For a better word, its like Acheron except a million time worst. If you never read through the Dark Hunter series, the book were written with you in mind. There are several parts from the previous novels to keep you updated with Styxx's life which sometimes I skipped (as I've read Acheron as a refresher a few weeks ago) and you'll still miss on a lot of things like the character dynamics and references which you'll get if you read through the series but Styxx is fine to be read as a standalone. 
 The book was chronicalized within the timeline during the birth of Acheron and Styxx around 9548BC to their childhood and young adult years until their death at the age 21 and setting between Night Embrace and Acheron and to the 2013-present time. If you've read Acheron, you'll be able to fill in most of the blanks Acheron had left. And because its a massive verse with added multiple mythology, it took a harder time to explain the entire story but its simple enough to explain. 
 Back in Atlantean pantheon, the head god, Archon and most of the gods and goddess have been trying to kill his unborn son (which he refuse to acknowledge) because of a prophecy from the Fates (his bastard daughters) who cursed Apostolos as the destroyer of the Atlantean pantheon. His Apollymi, the Goddess of Life, Death and Wisdom, was unable to prevent this from happening and she hid her son in the womb of a Greek Queen who gave birth to Acheron and Styxx. At this time, Archon recruited Bet'anya, the Goddess of Wrath, Misery & the Hunt to find Apostolos. 
 But at the moment when King Xerxes took notice of Acheron's silver eyes and he accused Queen Aara for sleeping with a god that he refused to consider his twins as his sons. With Acheron, he completely hate the child and refuse to acknowledge him as a son and he left Acheron at the age eight to his brother, Estes, in Atlantis where Acheron was being sexually abused, degraded and whored by his uncle. However, unbeknownst by anyone, his family treatments on Styxx was no more different than what they did on Acheron. Despite being a prince, he was forced to suffer under verbal and physical abuse by his mother, his sister and his father and add to that, Styxx have the ability to physically feel Acheron's abuses and like Acheron, he was also tortured by the voices from the Atlantean pantheon who was still searching for Apostolos among the mankind. Because of the voices and an accidental lapse, the king sent him to the Dionysion priests and Styxx undergo several weeks of painful "treatment" which left him scarred but called to the attention of Apollo who soon develop an unhealthy fascination on him. One day, Styxx tried to rescue Acheron in Atlantis but at his drugged state, Acheron called out to Estes and he captured Styxx and drugged him and uses this opportunity to sexually abuse Styxx as well. Once Styxx woke up, he was branded as a Tsoulus (whore) by his brother and during the months he's been incapacitated, Estes had used both of the twins and let others rape them mostly due to out of spite on Styxx. Because of Acheron's continuous drugged state, he never remember Styxx have ever tried to save it and because of him, Styxx began to steam in hatred on his beloved twin brother and especially his uncle. However, the nightmare didn't stop right there for Styxx as his uncle visits continue to haunt him. But his daily torments never end until he threw himself off a cliff and found himself stranded on a shore where he met a blind Egyptian girl who taught him how to love and beloved in return. And because of one stupid act of a god who killed his brother and unleash hell on the civilization when his death unleashed Apollymi and drag all of the civilization back to stone age and in return kill everyone he ever loved. 
 Note the prevailing theme of physical and sexual violence in my paragraphs. I don't know how anyone would mistake this for an average paranormal romance at this point. I've seen negative reviewers pointing out the extremes in this novel but frankly your average greek mythology aren't that sanitized for G-rated audience either. There's a lot of incest and rape in your garden variety mythology and its just as ridiculous to have Victorian censorship values on ancient mythology anyway. 
 And make no mistake, Styxx is not your garden-variety tortured alpha male. He grew up being hated by everyone just for being born as a prince, a brother and a son. Add to that, because of his bond with Acheron, he couldn't die normally and so he spend hundreds of century alone and mentally tortured by the gods which normally would drive anyone to insanity and psychopathy. He's been under all kind of abuse, degraded by everyone through the years and still he emerged like a phoenix rising from its ashes. If a book have the ability to wound you, Sherri's words does it all. 
 Unlike Acheron, the transition between the timelines was seamless and so was the romance element in this book. The story was layered in every possible of ways and its impossible to take this book simply because of the genre it sits. Its the story of a man being wronged by everyone and even the gods hate him for existing and his sanity persevered from his inner strength even if the world was undeniably cruel to him. In fact, you'd be a complete sadist or masochist if you enjoy the earlier part of the book. I think it did touch to Sherri's nerve with how recent romance literatures (New Adult and Young Adult) that seem to trivialized and romanticised abusive relationships. 
 Interestingly, the story provide us with another version of the situations in 'Acheron' through the eyes of another and that not everything is what it seems. Even we see Ryssa's temperament toward Styxx was different that what Acheron had perceived her and as the result everyone action on Styxx was cruelly unjustified. But it also brought us to the dynamics between Styxx and Acheron and how their relationship developed throughout the years that tested their brotherly bond through love, betrayal, isolation and forgiveness. 
 Without being a spoiler, as for the romance elements in this book, there were notably slightly unbalanced POV from Bethany. But the novel is still a Styxx-centered story and his undying love toward her is just as unpredictable and at times seriously have its own heartbreaking moments. But I'm definitely anticipating the future installments now that the stakes are definitely higher, pantheons broken apart and renewed. 
 Considered that I've been disappointed with the latest from Chronicle of Nick, I never doubt that Sherri would disappoint me again with this long long awaited book which I've waiting for years to read. Styxx have been an elusive character throughout the years among the Dark Hunters series and as much as I hated and loved his character, this book really did him justice and for all the genuine tears falling like a river from my eyes, Styxx is possibly the best book on the series to date. Balanced character, terrific storytelling, unpredictable and heartbreaking on the predictable part where you know it will happen and you can't stop Styxx from hurting.