A kiss and a kiss a kiss? That sounds like you might be asking about the ending of a specific book, but I'm not entirely sure which one. If you're referring to a story with a title that plays on repeated words like that, maybe it's a fanfic or a translated novel? Without knowing the exact title, I can only guess.
Often in romance or fantasy stories with such titles, a kiss can symbolize a sealing of fate, a magical contract, or a final, transformative connection. Endings might hinge on whether the kiss was literal or metaphorical, successful or tragic. I've seen some web serials where the 'third kiss' breaks a curse, for instance.
If you could recall more details about the plot or characters, it would be easier to pinpoint. My general thought is that narratives centered on a repeated act usually build towards its ultimate, perfected, or subverted iteration. The ending probably resolves the tension built around what each kiss means.