What are the major differences from the First Edition?

The major difference is the use of The Abbey Psalms and Canticles; the rest comes down to Word on Fire's unique design and layout.

"In November 2012, the U.S. Bishops voted to revise the translation of the Liturgy of the Hours in light of the Roman Missal, Third Edition and the 2001 Vatican document Liturgiam authenticam. The approval process was completed in November 2024, and on May 29, 2025, the USCCB transmitted the completed manuscript of the Liturgy of the Hours, Second Edition to the Holy See for confirmation."

(United States Conference of Catholic Bishops. Liturgy of the Hours, Second Edition. USCCB, usccb.org/prayer-and-worship/liturgy-of-the-hours/liturgy-of-the-hours-second-edition)