I'd also like to suggest another series of books. It's called "Your (6) Year Old" ... substitute the child's age. They're little paperbacks. Somewhat dated, but, child's organic physiology and development doesn't change with the times.
I find these books very useful to weed out what is typical behavior versus difficult child behavior.
DS will be 7 soon, and I've started the 7 year old one. He's typical already!
