Final answer:
The Nicholas Sparks book where both romantic partners survive is 'The Lucky One'. This deviation from Nicholas Sparks' usual formula offers a story where both leads, Logan and Elizabeth, achieve a joint future.
Step-by-step explanation:
The Nicholas Sparks book in which both romantic partners survive is 'The Lucky One'. In this novel, the main characters Logan Thibault and Elizabeth Green manage to find love with each other, and unlike many other Sparks' narratives, both characters do not face tragic ends but instead get a chance at happiness together. This book stands out in the Sparks' collection as it deviates from his typical formula where one of the romantic leads might meet a tragic fate.