Generally, I judge the strength of a book by a combination of how difficult it is to put down and how much effort it takes to slow down and let myself sink into the story and the language. It’s a difficult balance, after all, setting a reading pace when you can’t wait to see what happens next but you don’t want the story to end. Antonia Hayes debut novel “Relativity” scores a ten on both specs. Beautiful language, a few twists and turns, it is an emotional, compassionate and carefully crafted look at familial relationships, the lengths we go to protect someone from hurt and disappointment, and forgiveness (the seeking and the…