My teacher read us "A Wrinkle In Time" when I was in the seventh grade, about 1980. At the end of this book, there was one chapter from another book, sort of a promotional sample. It featured a fantasy warrior of some kind, standing on a plain, looking at an immense giant blob, a translucent wall that contained the half-digested remains of many other warriors, their armor and their weapons, spears and such. I always wanted to read that story, never found out the name. Ring any bells?
(Since it was at the end of the L'Engle book, I thought it might be by the same publisher Farrar, Straus and Giroux, but I don't know how to research it).