If you want Scott Hahn's take on what Opus Dei is all about, this is the book for you. More generally, if you want his take on a rich and fruitful spirituality for modern laity, this is the book for you.
That said, let me add a couple of observations.
First, the subtitle may be misleading. This is by no means a spiritual autobiography. There is certainly a personal dimension, in that Hahn is a member of Opus Dei, but the personal story serves more as a framework or a set-up for the theology.
Second, there's a "curious incident of the dog in the night-time" quality to the way he absolutely ignores all controversy involving Opus Dei. Several times as I was reading, I thought, "And now he'll mention and counter the well-known objection." But he doesn't. No doubt he gives no credence to the various controversies, but I don't think ignoring them altogether is the way to go in a popular introduction like this.