Everything in "Monomania" is missing something. The clock has no hands, the sky has no clouds, the tree bears no fruit, and yet time turns, the light dies, and something grows. The speaker lives in a world that has gone hollow but keeps running anyway, much like his own fixation.
At the centre is a failed proposal. He kneels, slips on the ring, and the bells and birds go quiet. He keeps asking "don't you hate me, darling?", which suggests he knows the one he's pursuing doesn't want him. Each chorus gives her a new label: scarecrow, sideshow, lotto. She goes from something frightening, to something to stare at, to a gamble he keeps betting on.
The mood is feverish and a little sad. The repetition ("no hands, no hands", "can't stop, won't stop") mimics a mind stuck in a loop. By the end, "can't stop" becomes "won't stop," and he seems to admit his obsession is partly a choice.