In this video clip, Douglas Wilson recommended this parenting book. I am 2/3s done and it has not been a disappointment. It is straight and to the point - but biblical and to the heart. I bought it used on Amazon Marketplace for 11 cents (plus shipping).

He gives four reasons we need to discipline our children:

1) The nature of the child demands correction.

2) The direction of the child demands correction.

3) The responsibility that God has placed on us as parents demands correction.

4) The love that we as parents have for our children demands correction.

His discussion concerning God's authority in our discipline is very good.

Parents, this is a really helpful book that you can read in a couple sittings (and then will refer to it often). 

Ask Doug - Advice on Childrearing from Daniel Foucachon on Vimeo.