I finished reading the book last night.
The majority of the essays are discussing the effect that Tolkien's the Lord of the Rings had on these writers and their writng style, but a few of them stand out:
Rythmic Patterns in the Lord of the Rings, by Ursula K. Le Guin.
This essay looks at the patterns of poetry and speech in the Lord of the Rings, right down to the patterns of events.
Tolkien After All These Years, by Douglas A. Anderson.
This essay looks at the other books on or by Tolkien, such as the HoME and Silmarillion. I think that this is also the one that looks at Tolkien's critics. Frankly, it was my favourite of them all.
I haven't read many of the authors who wrote these essays, but some of them look interesting, particularly Harry Turtledove.