Of course. That's not the focus of The Fellowship, of course: The topic only comes up a few times. But that's one of the little details I'd not known. Like the little detail that Swann proposed an opera based on Perelandra. No, I can't imagine how that would work. Even setting aside the distracting costume problems, how on Earth do you make music for that?
The book ties together the lives of Tolkien, Lewis, Williams, and Barfield before, during, and after the Inkling flourishing (it kept on with different members for years). They were none of them perfect (poor Williams, trying to do magic...) -- very far from it -- but they were dedicated to literature and to writing to catch the imagination.
Barfield is the odd duck here. He had to drop out to spend 30 years in a law firm. As the others died off he came back into a role as a link to the rest and a writer and lecturer. In pre-Internet days I learned of his participation in the Inklings (and the claim that he was the brightest of them all) and figured that if I liked T/L/W so well, I needed to read Barfield. I trotted down the the university library and brought home a book of his and sat down to enjoy -- what in blazes is this?
Anthroposophism was his thing, and evolution of consciousness and challenges to the nature of knowledge and I gave it up as a very bad job after about a chapter and a half. I gather from The Fellowship that Lewis didn't take Anthroposophism seriously and that this wounded Barfield deeply. I fear that I would have been less tactful.
I didn't know how painful writing LOTR was, and it hadn't occurred to me how old they all were by the time the last book came out.
The authors consider some of their contemporary writers to have been better stylists, but ... The local NPR station plays "art songs" sometimes. I've never liked them. Plenty of skill, but something's missing.
You don't need this book to appreciate the Inkling's works. But if you want to know about them this is a good choice.