Eight short lines, and almost all of them are somebody else's words. In "too late," the speaker barely speaks. Three times she reports what "he" told her, and only in the last couplet does she answer. The poem is about advice about love that comes after the moment for acting on it has passed, and about the quiet, stunned irony of that delay.
The structure does most of the work. The first three couplets begin with the same phrase, "he told me," and that repetition has the steady rhythm of someone being lectured. Each instruction is more urgent than the last: "go with him if you really love him," then "he wouldn't leave if he loved you," then "go before it's too late." There is no end rhyme and no decoration. The lines sound like speech, and the poem is better for it. A rhyme scheme would make the advice sound neat and wise, but here it sounds pressing, a bit tangled, and well-meant.
The advice itself is oddly contradictory, and that is easy to miss. The first line tells the speaker to follow someone if she loves him. The second says that if he loved her, he wouldn't be leaving at all. Both are tests of love, both framed with "if," and they point in opposite directions. The poem never says which the listener should believe, and it doesn't need to. The speaker is hearing confident opinions about her own feelings, and she can't be sure which of them to trust. The word "really" in the first line adds to the pressure, since it suggests that love is something she must prove.
Then comes the turn. "Little did he know" is a storyteller's phrase, the sort of line that sets up a twist. Using it here gives the speaker a slightly distanced, even wry tone, as if she is stepping back to watch a small tragedy of timing. The sentence is also the only one in the poem with a comma, and the poem's only full stop arrives at the very end, after "you already left." Until then the lines run on without punctuation, like a stream of remembered voices. The final period closes the matter.
The most interesting change is in the pronouns. Up to now, "you" belonged to the reported speech, where "he wouldn't leave if he loved you" addresses the speaker. In the last line "you" shifts. It might now be the person who has gone, spoken to directly at last. It might be the speaker's own earlier self. The poem doesn't say, and that ambiguity makes the ending more haunting. Either way, "left" lands hard against "leave." The earlier verb was hypothetical ("wouldn't leave"), and the final one is finished and past. The word "already" carries the poem's whole point: while everyone was debating what should happen, it had happened.
There is very little imagery in the usual sense, no weather or objects or scenery. What the poem has instead is motion. "Go," "leave," and "left" are all verbs of departure, so the poem reads like a doorway the reader never sees. The white space between couplets works like time passing, and the gap before the last couplet is the longest silence in the poem. The title, "too late," is also taken from the third "he told me" and so means two things. In the advice it is a warning, and in the ending it is a fact.
It is also worth noticing that the speaker never says "I." She appears only as "me," the object of everyone's instructions, and the lowercase style suggests someone small-voiced and tired. Her one independent statement comes in the final line, and it isn't an argument or a complaint, only a correction delivered with deflating calm.
The poem is significant because it takes a very familiar feeling, hearing the right advice when it is useless, and compresses it into a few seconds of reading. It doesn't explain its own sadness or tell the reader how to feel. It trusts the repeated phrase, the shifting pronoun and the closing full stop to do that, and the effect lingers well past the eight lines.