Among the eight two-part stories in Knight Terrors: Knightmare League, you will find four of them also collected in regular series books proper. That’s good in the sense that at least these stories are so tied in as to warrant inclusion in their own books as well as here; it’s unfortunate, of course, in that you’ll have to double dip to get half of this book’s original content.
Would that I could tell you that you can skip Knightmare League, that the best of this book you could read elsewhere, but that’s not the case. This book’s “original” tie-ins aren’t likely essential to the ongoing DCU, but they did present some of Knightmare League’s finest material.