The title promises glamour, but the poem delivers emptiness. Its "fortunate lovers" seem to have everything, yet they lie "as empty / as a castle in a box." That image is a clever one: a castle in a box sounds like a toy or a model, something with the shape of grandeur but nothing living inside. The speaker seems to be looking at a couple who are admired for their luck and finding them hollow.
The second stanza is harder to pin down. "Who he was she was" reads as if the lovers have dissolved into labels, just names and roles. "A pretty snare and hum" suggests an attractive trap with a pleasant background buzz, like celebrity gossip or a glossy surface that catches people. The final line, "which wonder at nothing," could describe the lovers themselves, or the audience, as incurious and numb. The mood is cool, ironic, and quietly critical, as if the speaker is watching a show and seeing straight through it.