A library is usually a place where things feel settled: books are printed, bound, shelved and numbered. So it is a small surprise that the speaker of "Book" claims to be one and, in the same breath, admits to being unfinished. In three short lines, the poem sets a proud boast beside a quiet confession and lets the reader decide which weighs more.
The central idea is that a mind, or a person, is not something you ever complete. The speaker begins with a metaphor, "I am a library", and the line is blunt and confident. The second line, "full of books and knowledge", keeps up the boast, moving from the concrete (books) to the abstract (knowledge), from the objects on the shelves to what they hold. Then comes the small word that turns everything around: "but". What follows, "I am never complete everyday", undercuts the picture of fullness. The poem separates two words we normally treat as close relatives. You can be *full* and still not be *complete*. A shelf can be packed and a gap can still remain, because the gap lies in what hasn't been read, written or understood yet.
The construction supports this. There is no rhyme and no punctuation, not even a full stop at the end, so the three lines read like one breath that never quite closes. That open ending suits a poem about incompleteness. The rhythm does similar work. The first two lines are almost identical in length, about six syllables each, like two shelves of equal height, orderly and sure of themselves. The third line stretches to around ten syllables and runs past the pattern the first two had set up. The line does what it says: it won't stay within its limits. Even the sounds quietly tie the claim to its undoing, since "books" and "but" share their opening sound, as if the boast already contained the thing that interrupts it.
The last word deserves a slower look. "Everyday" is written as one word, which gives it two possible readings. Read as "every day", the line says the speaker is not finished on any given day, because the library is always taking in more. Read as the single adjective "everyday", meaning ordinary, it suggests that incompleteness is simply a normal condition, nothing dramatic. The poem never settles this, and the ambiguity is useful. It leaves open whether the tone is frustrated or accepting. "Never complete" can sound like a complaint, but a library that was complete would also be a library that had stopped growing.
The title adds another layer. It says "Book", singular, while the speaker calls itself a library, plural in everything but name. One reading is that a single book can be finished (it has a last page), but a library cannot. By choosing the bigger metaphor, the speaker picks the form that has no final page. The title might also suggest that each "book" in the library is one piece of the self, and the poem is one page among many. The poem doesn't confirm either reading, but both fit its logic.
The name attached to the poem, Fallen angel, is worth a brief mention, though only as a suggestion. In a long cultural tradition, the idea of a fall is tied up with the pursuit of knowledge, and a poem that pairs "knowledge" with a restless sense of lack sits comfortably next to that name. This is an association a reader might make, not a fact about how the poem came to be written, and the poem gives us no details of setting or circumstance.
What makes the poem worth reading is how much it does with so little. It avoids both bragging about being well read and complaining about not being enough. Instead it treats learning as something that happens in the present tense, again and again. For students, who are often told to "fill up" with knowledge for an exam and then be done, it offers a different picture: the shelves are never full enough to stop adding to them, and that is the nature of a mind rather than a failure of it.