In particular, The Evolution of Walt Whitman inaugurated the study of Leaves of Grass as a lifelong work in progress, and it marked the end of the habit of talking about Leaves as if it were a single unified book. Asselineau saw Whitman's poetry “not as a body of static data but as a constantly changing continuum whose evolution must be carefully observed.” Throughout Evolution, Asselineau placed himself in the role of the observer, analyzing Whitman's development with a kind of scientific detachment. But behind this objective persona burned the soul of a risk taker who was willing to rewrite Whitman studies by bravely proposing what was then a controversial biographical source for Whitman's art—his homosexual desires.
The Evolution of Walt Whitman is a reminder that extraordinary works of criticism never exist in and of themselves. In this expanded edition, Roger Asselineau has provided a new essay summarizing his own continuing journey with Whitman. A foreword by Ed Folsom, editor of the Walt Whitman Quarterly, regards Evolution as the genesis of contemporary Whitman studies.