What are the essential qualities of a great relationship?Scientists and academics have spent entire careers investigating the nature of relationships,dating,and marriage,yet their findings are inaccessible to ordinary people,hidden in obscure journals read only by other academics.Now the bestselling author of The 100 Simple Secrets of Happy People and The 100 Simple Secrets of Successful People has collected the most current and significant data from more than a thousand studies on relationships,and spells out the key findings in plain English.