It’s a common experience for bookworms: You buy a new novel or nonfiction title and place it on your shelf or nightstand, but then you don’t actually read it.
Instead, that book joins a growing pile of texts waiting patiently to be picked up. The reading materials might sit in neat stacks, spill off shelves or gather metaphorical dust on a Kindle, but their unread reality remains the same.
In Japan, there’s a term for this phenomenon: tsundoku.
What is tsundoku?
“In general, tsundoku (積読) means piling up books that were bought out of curiosity but have never been read or will be read sometime in the future for various reasons,” Yoshihiro Yasuhara, an associate teaching professor of Japanese studies and Japanese coordinator for the Department of Languages, Cultures and Applied Linguistics at Carnegie Mellon University.
He noted that the term appeared in published writing around 1880 “with a comic connotation.” According to writer Mori Senzo, a satirical text around that time described a teacher with a large collection of books he had not read as a “tsundoku sensei.”
The word is understandably a favorite for many book lovers, offering a poetic, self-deprecating way to describe that towering “to be read” pile. But in Japanese, tsundoku isn’t just a quirky internet term. It’s a real word with a fascinating linguistic and cultural history.
“Tsundoku today is used as a noun meaning the habit or state of piling up books with the intention ― sometimes fulfilled, sometimes not ― of reading them later,” said Kiyono Fujinaga-Gordon, a linguist specializing in historical and Japanese linguistics and assistant teaching professor of Japanese studies at Carnegie Mellon University. “The term originates from the verb phrase tsunde-oku (積んでおく), literally ‘to pile something up and leave it there.’”
Yasuhara pointed to a sort of play on words with the term as well.
“The second character (読 doku = ‘to read’) of tsundoku sounds similar to ‘deoku’ of tsunde-oku,” he said.
So, as with many aspects of language, the tsunde-oku verb phrase underwent a linguistic evolution over time. The result was tsundoku as a description of a behavior or phenomenon.
“It is noteworthy that tsundoku can still function as a verb phrase in Japanese, but its pitch accent changes when used as a noun,” Fujinaga-Gordon. “This shift in accent reflects how the phrase has lexicalized and taken on a new grammatical and semantic status in contemporary Japanese. The form can still function verb-phrase-like in Japanese, but the widespread nominal use ― ‘a case of tsundoku’ ― is what English borrows.”
Is it a good or bad thing?
“Tsundoku likely started as a neutral description of an action ― simply ‘piling up and leaving books,’” Fujinaga-Gordon said. “Over time, as it became a noun describing a social behavior, it began to acquire evaluative overtones.”
Today, the word tsundoku seems to carry fluid connotations in Japan.
“When I read Japanese blogs and social media, I do see tsundoku used in positive, neutral, and negative contexts,” Fujinaga-Gordon said. “There are cases where it conveys mild shame or guilt, and others where it’s used humorously or even proudly as a sign of intellectual curiosity.”
So the question of whether tsundoku is a positive or negative thing might come down to whom you ask. You might find those embracing a little affectionate self-mockery over their unread stacks or even romanticizing the practice ... or those who are a little more judgmental.
“Even within Japan, people’s views differ,” Fujinaga-Gordon said. “For some, tsundoku is a charming quirk; for others, a symbol of procrastination or consumer excess.”
Yasuhara agrees the phenomenon can go either way.
“In my view, it could be both positive and negative,” he said. “It is positive if anyone can’t ignore an urge to buy any book that speaks to them even though it is not immediately read. It is part of an intellectual activity!”
He added that he is rather tsundoku-inclined himself.
“That said, I think many use tsundoku as a negative activity because those people are not really book lovers and purchase books for a purpose ― e.g., research, homework, business ― and yet procrastinate reading them as a sign of laziness or lack of momentum,” Yasuhara said.
Outside Japan, the term tsundoku has resonated with readers who see their book piles not as failures but as potential ― a concept echoed by Italian writer and philosopher Umberto Eco. He famously kept a vast library with tens of thousands of books, mostly unread, and coined the term “antilibrary,” which was later popularized by essayist Nassim Nicholas Taleb.
The underlying idea is that a collection of unread books can show curiosity, humility and ambition in the face of knowledge. It’s a monument not to what you already know, but to the infinite things you don’t.
In that light, tsundoku becomes almost aspirational. Rather than symbolizing guilt, your unread books might represent a form of optimism ― a belief that you’ll keep growing, learning and eventually getting around to that novel or history tome that called to you from the shelf.