Maybe in another life

"Hannah Martin's life isn't shaping up into much of anything. Since graduating college eight years ago, she has lived in six different cities and held countless meaningless jobs ... She takes up residence in her best friend Gabby's guest room. Along with Gabby and Gabby's husband Mark, [she goes] out to a bar where they meet up with some of [their] old friends, including Hannah's high school boyfriend, Ethan. Shortly after midnight, Gabby asks Hannah if she's ready to go. But then Ethan offers to give her a ride later if she wants to stay. Hannah hesitates. What happens if she leaves with Gabby? What happens if she leaves with Ethan? [This book] is told in two concurrent storylines following the consequences of each choice"--