This book follows Hugo, a Brit who is uncertain about the future path he's supposed to take (he's the youngest of a set of sextuplets - one of a six pack, according to the university that gave them all scholarships when they were born), on his journey across America in a train, with a girl he's never met. Mae is an aspiring filmmaker floundering after a rejection from her dream school. They only need each other as a way to get across the country, but they end up finding much more than they expected. 

This book is more than just a whirlwind romance story though, as it's really a study on love just as the title says. It's explored through many characters and their versions of love - toward each other and towards Mae and Hugo. All of the supporting characters are just wonderful and add so much to the story - Mae's dads, her beloved Nana, Hugo's brothers and sisters, and everyone they meet on the train. Really sweet and heartwarming YA romance that never feels either sickly sweet or too mature for YA.