Phantastes, by George MacDonald; The Everlasting Man by G. K. Chesterton; The Aeneid, by Virgil; The Temple, by George Herbert; The Prelude, by William Wordsworth; The Idea of the Holy, by Rudolf Otto; The Consolation of Philosophy, by Boethius; Life of Samuel Johnson, by James Boswell; Descent into Hell, by Charles Williams; Theism and Humanism, by Arthur James Balfour.
The list appears in Walter Hooper, C.S. Lewis: A Companion & Guide (p. 752) and originally appeared in The Christian Century (6 June 1962).