Drew first briefly and very helpfully addresses the questions of calling - what it is and Who is calling, before chapters in sections using Biblical Theology to guide the reader through the application of those great categories of Creation ("A Quest with a built-in purpose"), Fall ("Something wrong with every step"), Redemption ("Help along the way") and Consummation ("The View from the Top"). In every chapter within those sections he unpacks the Scriptural truth, helps us to identify with it with good interaction with literature, film and music, as well as life-stories from his church in Manhattan, and provides questions for reflection and discussion. Thoroughly in the reformed school, he doesn't shirk from a juicy Calvin quote when appropriate, but in his easy-to-read style of engagement this wouldn't cause anyone unfamiliar with such to stumble!
Now, the inevitable comparison with Purpose-driven (TM) Life, etc: where Warren sets his own agenda, filled with out-of-context one-line quotations from his many Bible translations of choice, each time chosen only to contain purpose, Drew's whole structure is driven by Biblical Theology, and each chapter unpacks the truth of a passage of Scripture quoted at the start of that chapter. This produces something much more Biblical than a badly-done word study will ever do, and something a lot more over-archingly God-centred than you do by starting a book which is all about you, by saying, "This is all about God." All the merits of Warren are to be found here in greater richness, with none of the demerits.
In brief, a very helpful book for what it says: finding your purpose in this world. Anyone could read it, especially as he takes a first short chapter to address what type of universe we live in - closed or open? - to introduce the idea of God as relates to purpose. From then on though, the hardened sceptic would be better to turn to Keller's A Reason For God before they'd be up for engaging with this. And after all, Keller then highly recommends Drew!