I have always been surprised by the relative lack of authoritative information on the development of twins. This is truly the most informative book on twins that I've found (and, as a psychologist and mother of twins, I was motivated to really look). There are other 'how to raise twins' books, but this book provides a more complete understanding of the development of twins. Be aware, though, that it is more scholarly than most-- not an 'easy read', nor does it provide many simple answers to everyday questions.