Which sentence is correct? "Do you want to know what is it about?" or "Do you want to know what it is about?"

Question

Which sentence is correct: "Do you want to know what it is about?" or "Do you want to know what is it about?"

I am having a discussion with my partner. I think it's the first one, she thinks it's the second one because we ask "what is it about?". But in my opinion those are two different structures.

Answer 1

The word order of a question (Who...? What...? When...? Where...? Why...? How...?) shows subject-verb inversion—

Why are _{finite verb} you _subject sad?

But a clause with one of those interrogatory words at its head, when it is standing as the answer to a question, will show normal word order:

How is it done? ^{inverted order}
-- She will show you {how it is done ^{normal order}}.

Such a clause is a proxy for the answer:

Does she want to know {something}?
—Yes, she wants to know {what it is about}.

What is it about?
—Bacteria in zero-gravity conditions is {what it is about}.

{Bacteria in zero-gravity conditions} = {what it is about}.

Only when you are asking the question or quoting the question verbatim do you use subject-verb inversion with these interrogatory words, because then you are asking the question or repeating the question exactly as it was asked, not paraphrasing it:

Does she want to know {something}?
—Yes, I will repeat her question. She asked, "What is it about?"

Answer 2

In an interrogative sentence when it's not embedded in another question we invert the verb and subject and in an embedded question we don't:

• What is it about? (Interrogative sentence with subject and verb inversion; no embedding)
• Do you want to know what it is about? (Embedded question within an interrogative sentence without subject and verb inversion)

The first sentence "Do you want to know what it is about?" is the correct one.