Let's say you are watching a video clip, then while watching, there is a portion that suddenly reminds you of a book. You know that book but you can't recall its name. And you say:

"I can't remember what book is that''


"I can't remember what book was that

Which is correct between them?

2 Answers 2


I can't remember what book that is.

I can't remember what book that was.

Both is and was are grammatically correct (the choice would depend on what that refers to in context) but the word order in the clause must be as above.

One of these books has a treasure map in it. What book is that?
--I've seen it, but I cannot remember what book that is.


You were telling me when we last met about a book you had once read that had a profound impact on you. What was its title again?
--I cannot remember what book that was. There have been many such books!

  • Excellent! My face just lightened up coz' this is a useful phrase, more likely you could use it often in the future.
    – John Arvin
    Aug 29, 2018 at 17:24
  • 1
    Also, it's common to use "it" rather than "that" in statements like this. "I can't remember what book it is."
    – Barmar
    Aug 29, 2018 at 23:21

What book is that? = is a question form in English. It is interrogative.

I can't remember what book that is/that was.

If you are making a statement, you would not use the interrogative form in a sentence. You have to use a phrasal object.

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