“I’m of the opinion that the real is imagined and the imagined is quite real,” Colum McCann has said in an interview. It’s a notion this novel, the follow-up to his 2009 National Book Award-winning Let the Great World Spin, fully embraces. As the title suggests, it’s about crossings, in particular between Ireland and either the United States or Canada (McCann himself is Irish but lives in New York City). There are three fictionalized renderings of actual events: Alcock and Brown’s historic first nonstop trans-Atlantic flight, from Newfoundland to Ireland, in 1919; abolitionist Frederick Douglass’ 1845 visit to Ireland, where he found that the potato blight was causing hardships worse than those American slaves were suffering; and Sen. George Mitchell’s successful 1998 mediation of the Good Friday peace agreement in Northern Ireland. Woven into these fascinating accounts are the stories of four generations of remarkable women in one family who also cross the Atlantic and whose lives are made to intersect with those of the historical figures. It’s a complex fabrication that could have spun out of control but doesn’t, and the result is a series of richly textured and often moving intertwined portraits, some historical, some fictional, but all utterly real.