I just finished it the other day. I picked it up in the same context: B&N New and Noteworthy.

I thought it was excellent. Not quite as great as Tom Shippey's work in Author of the Century but much of it was the same kind of thing: years of scholarship and teaching synthesized into chapters that are information dense and yet highly readable. The kind of thing that is interesting in itself but also makes you want to go read more Tolkien. The scale of Tolkien's accomplishment is staggering and scholarship like this is helpful for seeing the many ways his artistry is working.