Anybody who’s much around me or heard me give talks, will know I’m good for a quote from AW Tozer, at least every other outing!  Several of his books are still in print, and many recently republished as a series of ‘classics’.
The Pursuit of God consists of 10 short chapters, making it very accessible even to those who are not big readers. The key idea is whether we really hunger after God. He asks us how serious we are about wanting God, and whether we, like Abraham are willing to give up everything.

“The world is perishing for lack of the knowledge of God and the church is famished for want of His presence.”

“The way to a deeper knowledge of God is through the lonely valleys of soul poverty……… The blessed ones who possess the Kingdom are they who have repudiated every external thing and have rooted from their hearts all sense of possessing. These are the ‘poor in spirit.'”

“To have found God and still to pursue Him is the soul’s paradox of love, scorned indeed by the too-easily-satisfied religionist, but justified in happy experience by the children of the burning heart.”

or this, “The only Christian you want to listen to is the one who gives you more of a hunger for God!!” 

Tozer warns that it is possible to believe in God without knowing him in personal experience, and insists that we are able to experience his presence. God is of course present everywhere, but our problem is a lack of receptivity toward him. Each chapter closes with an earnest prayer asking God to change us and meet with us. There is much wise and insightful material in this short book, but its chief strength lies in its challenge to take seriously the pursuit of God. You might not need a lot of time to read it, but there is no point if you are not also willing to devote some time to self-examination and time alone with God in prayer.