The poem opens with a famous saying, "Ignorance is bliss," but strips it down to a single word in quotation marks: "Bliss." Then it pulls the rug out. Nothing is bliss, the speaker says, and the repeated word starts to feel slippery. Does it mean that bliss doesn't exist at all? Or that emptiness itself is the only kind of peace on offer?
The speaker rejects both easy options. Ignorance isn't bliss, but intelligence isn't either. Knowing more doesn't help, and neither does knowing less. That leaves a bare, cornered feeling, as if every route to happiness has been checked and found closed.
The mood is flat, weary, and a little bleak, though there's a dry wit in how neatly the lines turn the old saying against itself. The short, clipped lines and the final "Nothing." sit like a door closing. Whether the speaker is despairing or just calmly unimpressed is left for the reader to decide.