At the end of Amina Cain’s 2020 novel Indelicacy—a tale of art admired and ambiguously attained—the narrator says: “Sometimes I am immersed in my writing, ecstatic; sometimes I am only able to write one paragraph. On certain days I hate that paragraph.” Who doesn’t? Nothing so vexing as the writer who claims to spend a few blithe morning hours at the desk, then a guilt-free afternoon of tennis or whatever. In A Horse at Night: On Writing, a shifting, elliptical essay on the writing life, Cain admits the crushing heaviness of composition, and the airy fantasies that attend it.