The Duties of Parents by JC Ryle - it's a simple and short read but jam-packed with truth and wisdom. I find myself referencing back to it often - hence the well-loved wrinkles given to my copy!
This is one of our favorite books, we think its a must-read for parents desiring to biblically disciple their children. Wonderfully enough, it has been made available as a free PDF! Below is the book's introduction and at the bottom, you will find a link to download the e-book from monergism.com
Train up a child in the way he should go; and when he is old, he will not depart from it." Proverbs 23:6.
I suppose that most professing Christians are acquainted with the text at the head of this page. The sound of it is probably familiar to your ears, like an old tune. It is likely you have heard it, or read it, talked of it, or quoted it, many a time. Is it not so? But, after all, how little is the substance of this text regarded! The doctrine it contains appears scarcely known, the duty it puts before us seems fearfully seldom practiced. Reader, do I not speak the truth? It cannot be said that the subject is a new one. The world is old, and we have the experience of nearly six thousand years to help us. We live in days when there is a mighty zeal for education in every quarter. We hear of new schools rising on all sides. We are told of new systems, and new books for the young, of every sort and description. And still for all this, the vast majority of children are manifestly not trained in the way they should go, for when they grow up to man's estate, they do not walk with God. Now how shall we account for this state of things ? The plain truth is, the Lord's commandment in our text is not regarded; and therefore the Lord's promise in our text is not fulfilled. Reader, these things may well give rise to great searchings of heart. Suffer then a word of exhortation from a minister, about the right training of children. Believe me, the subject is one that should come home to every conscience, and make every one ask himself the question, "Am I in this matter doing what I can?" It is a subject that concerns almost all. There is hardly a household that it does not touch. Parents, nurses, teachers, godfathers, godmothers, uncles, aunts, brothers, sisters,—all have an interest in it. Few can be found, I think, who might not influence some parent in the management of his family, or affect the training of some child by suggestion or advice. All of us, I suspect, can do something here, either directly or indirectly, and I wish to stir up all to bear this in remembrance. It is a subject, too, on which all concerned are in great danger of coming short of their duty. This is preeminently a point in which men can see the faults of their neighbors more clearly than their own. They will often bring up their children in the very path which they have denounced to their friends as unsafe. They will see motes in other men's families, and overlook beams in their own. They will be quick sighted as eagles in detecting mistakes abroad, and yet blind as bats to fatal errors which are daily going on at home. They will be wise about their brother's house, but foolish about their own flesh and blood. Here, if anywhere, we have need to suspect our own judgment. This, too, you will do well to bear in mind. As a minister, I cannot help remarking that there is hardly any subject about which people seem so tenacious as they are about their children. I have sometimes been perfectly astonished at the slowness of sensible Christian parents to allow that their own children are in fault, or deserve blame. There are not a few people to whom I would far rather speak about their own sins, than tell them their children had done anything wrong. Come now, and let me place before you a few hints about right training. God the Father, God the Son, God the Holy Spirit bless them, and make them words in season to you all. Reject them not because they are blunt and simple; despise them not because they contain nothing new. Be very sure, if you would train children for heaven, they are hints that ought not to be lightly set aside.