“Their book” is a possessive phrase that causes more confusion than it should. The word “their” is a possessive determiner, so “their book” means the book belonging to them . The confusion arises because “their” sounds identical to “there” and “they’re,” and because the phrase has picked up unrelated slang and news meanings. This guide explains the grammar clearly, shows the common mistakes, and flags the other contexts where you might encounter the phrase.

The Grammar: What “Their Book” Actually Means

“Their” is the third-person plural possessive determiner. It indicates that something belongs or relates to a group of people, animals or things that have already been mentioned .

So “their book” means the book belongs to them. The Free Dictionary gives the simplest example: “It is their book” . Collins Dictionary gives a similar structure: “Janis and Kurt have announced their engagement” . The pattern is the same: “their” points back to a previously mentioned group, and the noun that follows is the thing that belongs to that group.

There is a second, increasingly common use. “Their” can also refer to a single person when you do not know or do not want to specify their gender. Cambridge Dictionary gives the example: “One of the students has left their book behind” . In this case, “their book” means the book belonging to one student, whose gender is unspecified.

That second use is grammatically standard in modern English. It is not a mistake. Collins Dictionary notes that it is used “instead of ‘his or her’ to indicate that something belongs or relates to a person without saying whether that person is a man or a woman” .

The Three Words People Confuse

The confusion around “their book” is almost always a confusion between three homophones. They sound the same but mean different things.

The practical test is substitution. If you can replace the word with “they are,” use “they’re.” If you can replace it with “belonging to them,” use “their.” If you are pointing to a place, use “there.”

The News Story: A Book Withdrawn Over Edits

In October 2026, “their book” appeared in headlines for a specific reason. Alana Hadid and Jenan Matari withdrew their book about Palestine for young readers from Random House after a dispute over editorial changes .

The disagreement centred on a passage about the October 7 attacks. The authors argued that people under colonial domination have a right to resist. Random House added a line stating that the attacks were a violation of international law. The authors objected and withdrew the book . A Tumblr post citing The Guardian reported that Interlink Publishing, a Palestinian-owned press, would publish the book instead .

This is a specific news event, not a general meaning of the phrase. If you encountered “their book” in a news context in October 2026, this is likely what it referred to.

The Betting Meaning: A Different “Book”

In betting slang, “book” has nothing to do with a bound volume. ESPN’s betting glossary defines “book” as short for “sportsbook,” a legal establishment where customers can place wagers . A “bookie” is a person who takes bets .

So if someone says “their book” in a gambling context, they mean the sportsbook they use, not a book they own. This is a separate meaning entirely, connected only by the shared word “book.”

The phrase “throw the book at someone” is another unrelated idiom. It means to punish someone as severely as possible, particularly in a legal context. Green’s Dictionary of Slang records it as a phrase meaning to impose the maximum penalty .

A Note on the Podcast Result

One search result referred to a podcast episode from October 2026 promoting a book called WTF America?!: The Way Out of This Hell and Back to Democracy by Ben, Brett and Jordy Meiselas . The podcast described the brothers releasing “their book” and promoting it. This is a straightforward use of the possessive: the book belongs to the Meiselas brothers. It is not a special meaning, just the standard grammar in a specific context.

Frequently Asked Questions

What does “their book” mean?

“Their book” means the book belonging to them. “Their” is a possessive determiner that refers back to a group of people or things already mentioned. It can also refer to a single person whose gender is unspecified, as in “One of the students left their book behind” .

Is it “their book” or “there book”?

It is always “their book.” “There” refers to a place, not possession. “Their” indicates belonging. “They’re” is a contraction of “they are” and cannot be used before a noun like “book” .

Can “their” refer to one person?

Yes. “Their” is widely used as a gender-neutral pronoun for a single person when the gender is unknown or irrelevant. Cambridge Dictionary gives the example “One of the students has left their book behind” . This usage is standard in modern British English.

What was the book withdrawn by Alana Hadid?

Alana Hadid and Jenan Matari withdrew their Palestine book for young readers from Random House in October 2026 after the publisher added a line stating that the October 7 attacks violated international law. The authors objected to the edit and withdrew the book. Interlink Publishing was reported to be picking it up .