Seven short lines, and the poem has already played a trick on us. It calls itself "Abstract," the name of the tidy summary at the top of a scientific paper, and then speaks in exactly that voice: "An experiment:". The colon promises method and result. The word has other meanings too. "Abstract" is the opposite of concrete, and as a verb it means to draw something out and take it away. All three meanings pull at what follows, though the poem never says which one it prefers.
The experiment itself is oddly gentle. "Hands talking, / we frighten the bear / back into a book." No weapon appears, only gesture, and the "we" is collective and a little playful, like children driving off a monster by pretending. The phrase "back into" implies the bear came out of a book in the first place, so it is a creature of fable or picture-book pages, and the people can make it retreat to where stories keep their animals. The line break after "bear" is worth noticing. For a beat the animal stands in open space before the next line sends it home. The scene is funny and a little tender, and the experiment seems to succeed.
Then the poem turns, with no transition. "The bills of mortality" were the printed lists of deaths and their recorded causes that London parishes produced, so the poem moves from a bear in a story to a bureaucratic ledger of real bodies. Here is a second kind of book. The bear has been put away in one, and the poem now opens another and reads that "appear to be full / of pure hunger." The cautious "appear to be" fits the hedging language of a research abstract, as if the speaker were reporting an unwelcome finding with scientific restraint. The line break after "full" gives that word a brief false meaning, satisfaction, before "of pure hunger" contradicts it. A book can be full of emptiness.
The poem never says the bear stands for hunger, but its structure invites the reading. The judgment is an inference, but a strong one: the bear is hunger given a body, and a body can be scared off. Hunger itself cannot. We can shoo the animal back into a story, but the ledger of the dead still holds what the animal stood for. "Pure" sharpens the point. Hunger is unmixed and unmetaphorical, with nothing to scare away. It is also the poem's most abstract word, since it takes a lived condition and lifts it off any particular person, as a list of causes of death does. The title seems to point at that loss: to abstract suffering into a number or a category is another way of putting it into a book.
There is no rhyme and no regular meter. The lines run three to six syllables, light and quick, which makes the poem sound like a note jotted down rather than a performance. Still, the sound is carefully tied together. The plosive b links "bear," "book," and "bills," so that the bills seem to be the next item in a series of books and bears. The first sentence closes on the hard stop of "book," neatly, like a lid. The last word, "hunger," is two syllables ending on an open, trailing r, and it does not close anything. The poem ends where the problem stays unresolved.
What makes it worth reading is how much it does with so little. In a few lines it asks what books are for. They can contain what frightens us, as the bear is contained, or they can count what we could not prevent, as the bills do. The poem is itself a kind of abstract, a summary of some larger story it declines to tell, and it may be a place where a bear can hide. The final line leaves us unsure whether that is a comfort or a warning.