Diga lo que diga la contraportada, quiero leer el prólogo antes de comprar el libro.

This is a very common Spanish pattern:

diga lo que diga = whatever ... says / no matter what ... says

The verb is repeated to create a concessive meaning: it shows that the result in the main clause does not change.

So here:

• Diga lo que diga la contraportada
  = Whatever the back cover says = No matter what the back cover says

This structure often uses the present subjunctive:

• haga lo que haga = whatever he/she does
• vayas donde vayas = wherever you go
• sea como sea = however it may be

So the repetition is not accidental; it is part of a set pattern.

Here it is the present subjunctive, not an imperative.

Why?

Because the sentence is not giving a command. It is using the pattern:

• diga lo que diga = whatever it says

The imperative diga would mean say! when speaking formally to usted, but that meaning does not fit here.

A good clue is the full structure:

• diga lo que diga + noun/pronoun

That strongly points to the concessive subjunctive pattern.

Lo que here means what or more literally that which.

In diga lo que diga la contraportada, it helps build the idea of whatever the back cover says.

You can think of it like this:

• lo que diga la contraportada = what the back cover says
• diga lo que diga la contraportada = whatever the back cover says

So lo que is not just random filler. It is the element that introduces what is said.

A useful comparison:

• Sé lo que dice = I know what it says
• Diga lo que diga = whatever it says

Spanish word order is more flexible than English.

The more neutral order would be:

• lo que diga la contraportada

Here the subject la contraportada comes after the verb diga, which is very normal in Spanish, especially in subordinate clauses.

In English, we usually prefer:

• what the back cover says

In Spanish, both verb-subject and subject-verb orders can appear, but after structures like this, verb + subject often sounds very natural.

Contraportada usually means the back cover of a book.

In practice, in a sentence like this, it often refers to the text on the back cover as well, such as the summary, blurb, or promotional description.

So:

• Diga lo que diga la contraportada
  is naturally understood as
  Whatever the back cover says / Whatever the blurb says

The subjunctive is used because this structure expresses indefiniteness and concession:

• the exact content of what the back cover says is not important
• the speaker’s decision remains the same anyway

So the meaning is:

• No matter what it says, I want to read the prologue first

Spanish often uses the subjunctive after expressions like:

• haga lo que haga = whatever he/she does
• donde vaya = wherever he/she goes
• como sea = however it is

The subjunctive here does not mean doubt in the usual simple sense; it is part of a fixed way of expressing regardless of what happens/is said.

Because after querer, if the subject stays the same, Spanish normally uses an infinitive.

Here the subject is I in both parts:

• quiero = I want
• leer = to read

So:

• quiero leer el prólogo = I want to read the prologue

You use querer que + subjunctive when the subject changes:

• Quiero leer el prólogo.
  = I want to read the prologue.
• Quiero que leas el prólogo.
  = I want you to read the prologue.

Because when antes de is followed by an infinitive, it means before doing something.

So:

• antes de comprar el libro = before buying the book

This is the normal structure when the subject is the same:

• Quiero leer el prólogo antes de comprar el libro.

If there is a new finite verb and often a different subject, Spanish uses antes de que + subjunctive:

• Quiero leer el prólogo antes de que compres el libro.
  = I want to read the prologue before you buy the book.

So the basic contrast is:

• antes de + infinitive
• antes de que + subjunctive

In book-related Spanish, prólogo usually means prologue or sometimes foreword, depending on context.

Very roughly:

• prólogo: a preliminary text before the main work, often written by the author or sometimes by someone else
• introducción: introduction; usually more explanatory, setting up the subject
• prefacio: preface; similar to English preface, though often less common in everyday use

In this sentence, prólogo is simply the named front section the speaker wants to read before buying the book.

Yes. That is actually one of the best natural translations.

A very literal breakdown is:

• Diga lo que diga la contraportada
  = Say what it may, the back cover
  which sounds unnatural in English

A natural English version is:

• No matter what the back cover says, I want to read the prologue before buying the book.
• Whatever the back cover says, I want to read the prologue before buying the book.

So learners should recognize that this is one of those Spanish structures whose meaning is clearer than its word-for-word translation.

Because Diga lo que diga la contraportada is an introductory subordinate clause.

It sets up the main statement:

• Diga lo que diga la contraportada,
• quiero leer el prólogo antes de comprar el libro.

In English, we also usually put a comma after an introductory clause:

• Whatever the back cover says, I want to read the prologue...

So the comma helps separate the concessive clause from the main idea.

Yes, absolutely. It is very useful to learn it as a pattern.

The general model is:

• [subjunctive verb] + lo que + [same subjunctive verb]
• meaning: whatever / no matter what

Examples:

• Haga lo que haga, no cambiaré de opinión.
  = Whatever he/she does, I won’t change my mind.
• Digan lo que digan, seguiré adelante.
  = Whatever they say, I’ll keep going.
• Pase lo que pase, llámame.
  = Whatever happens, call me.

If you learn it as a chunk, it becomes much easier to recognize and use.

It is perfectly normal. Spanish, like English, often lets objects such as books, signs, headlines, or labels act as the thing that says something.

For example, both languages allow this kind of idea:

• The sign says...
• The label says...
• The back cover says...

So la contraportada dice... is a natural personification, not an odd mistake.

Yes. A more expanded version could be:

• Aunque la contraportada diga cualquier cosa, quiero leer el prólogo antes de comprar el libro.

or

• Sea lo que sea lo que diga la contraportada, quiero leer el prólogo antes de comprar el libro.

But Diga lo que diga la contraportada is more idiomatic, compact, and elegant.

So the original sentence is a very natural way to say:

• Regardless of what the back cover claims, I want to read the prologue before buying the book.