A friend pointed out this abstract to me on the Resurgence.
What Piper might call Christian Hedonism, Lewis called Christian Eudaimonism. Both etymologically (pursuit of pleasure and pursuit of happiness) and substantively, they are strikingly similar if not identical.
Here's a bit from the abstract that roused me to courageous virtue in my personal pursuit of God:
A eudaimonistic perspective does not see ethics as a strictly separable domain of issues or rules, only extrinsically related to the overall aim of one's life. Nor, as Lewis points out, does it understand the ethical life as primarily negative or restrictive. Rather, a Christian eudaimonistic approach sees all of one's life, including the ethical life, as a positive, passionate pursuit of the Good worth ultimately seeking, which unifies and integrates all of life and ultimately satisfies one's deepest desires.