I'm not sure specifically as I haven't read this novel. But generally, a title like that might suggest a story about a betrayal that occurs during a wedding (at the altar) involving characters Rachel and Louis. It could be about broken promises, secrets revealed, or unfaithfulness that shatters their relationship at a very crucial moment.
The title 'Betrayal at the Altar: Rachel and Louis' novel indicates that Rachel and Louis are the main characters. Their relationship is likely to be the core of the story. Since there is a mention of betrayal at the altar, they are the ones who will experience the main conflict. Maybe they are lovers or fiancés, and something goes horribly wrong at their wedding, with them being at the heart of this dramatic event.
'God Devouring Tower' was a fantasy novel written by the author of the Setting Sun Era. The story was about the young Qin Yi who lost his heavenly pulse because he was framed. However, he accidentally obtained the peerless divine pagoda, awakened the ancient God-devouring bloodline, reconstructed the divine pulse, and cultivated the Supreme Law. Finally, he rose up in adversity and displayed his unparalleled elegance. The novel was currently being serialised. The latest chapter was chapter 116. The main character, Qin Yi, had left the Heavenly Sword Sect.