Four Quartets
Eliot's late masterwork and his greatest sustained achievement: four meditations on time, place, memory, and salvation structured as music (thematic development, variation, recapitulation). Where The Waste Land is despair, Four Quartets is something harder to name: acceptance tinged with terror. "Little Gidding" ends with "And all shall be well and / All manner of thing shall be well." The most religious and the most honest of his major poems.
Eliot interrupts his own lyric flights to concede they were unsatisfactory ways of putting it, and he is sometimes right. Long stretches are versified sermon, abstract where The Waste Land was vivid. If you cannot meet the Anglican theology at least halfway, the consolation of Little Gidding's ending stays locked behind doctrine.
The case for it and the rest of the canon open with Pro.
