THE TOP TEN REASONS TO KNOW CHRISTIAN HISTORY
Good little article from the Christianity Today website
Summary (quoted):

Reason 1 -- Christian history is everywhere in our culture. No matter what your religious background (or lack thereof), you just can't understand the modern, Western world—including its wars—unless you know your Christian history...If you live in America, or anywhere in the West, your whole environment is soaked in "leftover Christianity."

Reason 2 -- It liberates you from the tyranny of the present—and of the recent past.

Reason 3 -- Life is too short to learn by experience.

Reason 4 -- Whatever question is on your mind, someone smarter than you has already seen it clearer, thought about it longer, and expressed it better. Why reinvent the wheel? Also falling under this heading: There are no new heresies—only old ones in new clothes. And again, they've all been answered with more wisdom and erudition than we'll ever be able to muster.

Reason 5 -- Because the deeper our roots, the higher we grow. Believers are all part of a "Dead Christians Society." We have far more brothers and sisters in the faith who are no longer around than we do contemporary saints. Lets get to know them. And while we slog it out on earth as members of the Church Militant, the Church Triumphant is pulling for us from heaven.

Reason 6 -- Because reading Christian history is a great way to meet fascinating people and hear dramatic, colorful stories.

Reason 7 -- Because reading Christian history helps root out prejudice and foster sympathy and humility. It's so easy to think "The Church 'R' Us." It ain't. Most Christian believers look—and have looked, in past centuries—very different than we do. They've had different questions, different assumptions, different "lifestyles," different approaches to the Christian life, different strategies for evangelism, teaching, preaching, sacramental life, social action. . . .

...That's a good thing, because the church today is a body with a wide (and sometimes wild!) variety of members. Knowing more about the past, we gain insight into the practices and problems of other Christians in the present. We may become less critical of others—and even more aware of our own shortcomings and limited perspectives.

Reason 8 -- Because reading Christian history shows us how we got where we are today. Where did all those denominations come from? How did the distinctive beliefs and practices of my own church develop? What's the big deal over Calvinism and Arminianism?

Reason 9 -- Because . . . well, if reason 8 depresses you by reminding you of the disunity and dysfunction of the church, then consider this reason, too: We need to read Christian history to remind us of our mission.

Reason 10 -- We should read Christian history because Christianity is a historical religion, based on a historical person and the words of two "Testaments" full of historical accounts.