Sadly, this book fell well short of my expectations. I was hoping for some real insight into what makes a person tick. Instead, this book was more like a long, drawn-out horoscope.
The observations made by Dr. Leman are only that... observations. Very little effort is made to substantiate those observations with objective evidence. Indeed, lots of qualifiers are thrown in as a safety net. So that if his description of first-borns doesn't fit you, then you should think of it as only a guideline.
It's not that I got NOTHING out of the book. I did get a sense of the three basic personality types.
However, those personality classes are very difficult to apply. Why? Because his definition of who is in those categories is vague. You are a first-born if you are the first girl or first boy in your family, or if your next older sibling is at least 5 years older than you. Similarly, you are a last-born if you are the youngest in your family, or if your next younger sibling is a least 5 years younger than you. A middle child is one who doesn't fit those categories.
I have an older sister (15 months older), and a brother who is about 5 years younger. That makes me a first-born and a last-born. But in many ways, I also fit the definition of a middle child. How uninteresting is THAT?! Without a clear picture of what class you're in, the book descends into an arbitrary list of personality types, and my personality spans across all of them. Bleh.