Russell Moore recently blogged on "The Spiritual Warfare of Boring Preaching." It's good enough that you should read the whole article. However here are a few quotes to whet your appetite:
Satanic preaching is boring because the goal isn’t to engage people with preaching. It’s to leave the “desires of the flesh” alone, so that the hearers may continue in their captivity to the prince of the power of this air.
If lost people don’t like your message because they’re hostile to the gospel, you’re in good company. But if you’re boring the people of God with the Word of God, something has gone seriously awry. It may be that you preach just like the devil, and that you don’t even know it.
A sermonic information dump—with PowerPoint outline point by sub-point by sub-sub-point can “safely” distance your people from Christ. A sermon that simply collates and regurgitates what you’ve read in commentaries can make the Word of God a matter of cognition not submission. A strung-together list of life tips can make it easy for your people to disregard this word just like they disregard the weight loss plans commercials on television or the flossing ad campaigns they see from the dentist’s chair.
The devil doesn’t mind boring sermons, so long as you allow him to preach too. He doesn’t mind the Word being heard so long as it’s the appetites that really enliven his people. And he doesn’t mind the gospel going forward as long as God’s people hear his accusations of them (and they’re all expository and biblically-based!).
But if you grip people with the drama of the gospel of Christ, if you jolt them into seeing the ancient newness of the Word of God, then you’ll have a demonic insurrection on your hands.