Rachel Friedman has always been the consummate good girl who does well in school and plays it safe, so the college grad surprises no one more than herself when, on a whim (and in an effort to escape impending life decisions), she buys a ticket to Ireland, a place she has never visited. There she forms an unlikely bond with a free-spirited Australian girl, a born adventurer who spurs Rachel on to a yearlong odyssey that takes her to three continents,...