Thoughtless, written by S.C. Stephens, is a contemporary romance novel that features Kellan Kyle, a charismatic and controlling musician. The story revolves around the love triangle between Kiera Allen, her boyfriend Denny, and Kellan. Kellan's possessive and seductive nature adds tension to the story as Kiera finds herself torn between two men. The book explores themes of desire, jealousy, and the consequences of impulsive decisions.