Quiero preguntar cuáles son los libros más interesantes.

I want to ask which books are the most interesting.

Breakdown of Quiero preguntar cuáles son los libros más interesantes.

• yo: I
• querer: to want
• ser: to be
• el libro: the book
• interesante: interesting
• .: period
• preguntar: to ask
• más: most
• cuáles: which

Questions & Answers about Quiero preguntar cuáles son los libros más interesantes.

Why is it quiero preguntar and not just pregunto?

Quiero preguntar literally means “I want to ask”. It introduces an indirect question (a reported question), not a direct one.

• Pregunto: ¿cuáles son los libros más interesantes?
  = I ask: which are the most interesting books? (direct question, you quote the question itself)

• Quiero preguntar cuáles son los libros más interesantes.
  = I want to ask which are the most interesting books. (you talk about the question you want to ask)

In your sentence, you’re not actually asking the question yet; you’re stating your intention to ask, so quiero preguntar is natural.

Could I say “Quiero saber cuáles son los libros más interesantes” instead? What’s the difference?

Yes, that’s completely correct, and very common.

• Quiero preguntar… = I want to ask… (focus on the act of asking someone)
• Quiero saber… = I want to know… (focus on the information you want to have)

In real life, quiero saber is often more natural unless you really want to highlight that you’re about to ask someone a question. Both are fine grammatically.

Why is it cuáles and not cuál?

Cuál / cuáles agrees in number with the thing it refers to.

• cuál = which one (singular)
• cuáles = which ones (plural)

Here it refers to los libros (plural), so Spanish uses:

• cuáles son los libros más interesantes → which (ones) are the most interesting books

If it were singular, you’d say:

• cuál es el libro más interesante → which (one) is the most interesting book

Why cuáles son los libros and not qué libros son los más interesantes?

Both are possible, but there is a nuance:

• Cuáles son los libros más interesantes.
  Literally: Which (ones) are the most interesting books?
  This sounds like you have a specific, known set of books in mind and you want to know which of them are the most interesting.

• Qué libros son los más interesantes.
  Literally: What books are the most interesting?
  This focuses more on identifying or listing the books, less on choosing from a clearly defined set.

In many contexts they’re close in meaning, but cuáles son los libros is very natural when you’re thinking of a specific group (e.g. books in a course, on a list, in a collection).

Why does cuáles have an accent (cuáles) here?

The accent distinguishes interrogative/exclamative uses from ordinary relative pronouns.

• cuáles (with accent) is used in:

  • Direct questions: ¿Cuáles son los libros más interesantes?
  • Indirect questions: Quiero preguntar cuáles son los libros más interesantes.

• cuales (without accent) appears in non‑question relative clauses, for example (more formal):

  • Los libros, los cuales son muy interesantes, están en la mesa.
    The books, which are very interesting, are on the table.

In your sentence, it’s part of an indirect question, so it must be cuáles with an accent.

Why is it son and not sean? Shouldn’t an indirect question use the subjunctive?

No; in Spanish, indirect questions normally use the indicative, not the subjunctive, when you’re just asking for factual information.

• Quiero preguntar cuáles son los libros más interesantes.
  → You are asking about a fact (which books are the most interesting) → son (indicative).

The subjunctive sean would appear if there were doubt, desire, or some other subjunctive trigger, for example:

• Busco libros que sean interesantes.
  I’m looking for books that are interesting (they’re not identified; it’s more hypothetical).

But with preguntar + question word, you almost always use the indicative.

Why is there no question mark in Spanish around cuáles son los libros más interesantes?

Because this is an indirect question, not a direct one.

• Direct question:
  ¿Cuáles son los libros más interesantes?
  → Needs ¿ ?

• Indirect question:
  Quiero preguntar cuáles son los libros más interesantes.
  → The whole sentence is a statement about a question, so no question marks.

In Spanish, the ¿ ? symbols are only used for direct questions.

Why is it los libros and not just libros?

Spanish uses definite articles more often than English, especially when referring to a specific group.

• los libros = the books (a specific, identifiable set: maybe the books on a list, in a course, in a series, etc.)
• libros (without article) would sound like “(some) books” in a very general sense, and doesn’t fit as naturally with “which are the most interesting”.

Since you’re asking which books are the most interesting, you implicitly have some known group in mind, so los libros is appropriate.

Why is it los libros más interesantes and not los más interesantes libros?

In Spanish, most adjectives (like interesante) usually go after the noun:

• libros interesantes = interesting books
• libros más interesantes = more interesting books
• los libros más interesantes = the most interesting books

Putting the adjective before the noun (e.g. los interesantes libros) is possible but tends to be stylistic, poetic, or to give a slightly different nuance.
The structure “the most interesting books” is always los libros más interesantes, not los más interesantes libros.

Is los libros más interesantes a kind of superlative? How does that work?

Yes. This is a relative superlative: the most interesting books (among a group).

Spanish forms it like this:

• el libro más interesante = the most interesting book
• los libros más interesantes = the most interesting books
• la película más interesante = the most interesting film
• las películas más interesantes = the most interesting films

Structure:
article + noun + más + adjective

You don’t repeat the article: you don’t say los libros los más interesantes.

Could I just say ¿Cuáles son los libros más interesantes? without quiero preguntar?

Yes. That would turn it into a direct question:

• ¿Cuáles son los libros más interesantes? = Which are the most interesting books?

Your original sentence:

• Quiero preguntar cuáles son los libros más interesantes.

is more like meta-language (“I want to ask which…”) and would usually precede actually asking the question, or be used in more formal or indirect speech. In many real situations, people would just ask the direct question with ¿…?

Is quiero preguntar polite in Spain, or should I use something else?

Quiero preguntar… is not rude, but it can sound a bit direct in some contexts.

For more politeness in Spain, people often use:

• Quería preguntar… (imperfect)
• Quisiera preguntar… (conditional of querer)
• Querría preguntar… (also conditional, more formal/literary)

For example:

• Quería preguntar cuáles son los libros más interesantes.
• Quisiera preguntar cuáles son los libros más interesantes.

These sound softer and more polite, especially in customer service, academic, or formal contexts.

Is there any difference between preguntar and pedir here? Could I say quiero pedir?

You should use preguntar here, not pedir.

• preguntar = to ask a question, to ask for information

  • Quiero preguntar cuáles son los libros más interesantes.
    I want to ask which are the most interesting books.

• pedir = to ask for / request something (an object, a favor, an action)

  • Quiero pedir el libro. = I want to request/ask for the book.
  • Quiero pedir un favor. = I want to ask a favor.

Because you’re asking for information (which books?), preguntar is the correct verb.