Looks like you can get a new copy of this book for $300. I got it last February for $30, used, and have been picking away at it since with no great success. It is Charles Williams’ Arthurian poetry, along with an essay in the end. What I finally hit was the C.S. Lewis commentary, and it is some of the most exotic reading of anything he’s written I’ve done. The things these chaps were aware of! I think $300 would not be asking too much for the things one encounters there, not only in Lewis but once he’s put one on the track of things, in Williams’ poetry.
I recommend, if you want a recommendation, if you decide to get it, if you’re going to read it, I recommend you try some of the poems and see how far you can get. They’re obscure, but having an idea of what Lewis is talking about before going back and reading his commentary helps. Then read his commentary, then have at the poems, re-reading them as did W.H. Auden for the rest of your life. Long term project, I bet, assimilating all Williams envisioned.