Este libro me sirve para aprender español.

Here servir means to be useful, to be good for, or to serve for a purpose.

So Este libro me sirve para aprender español means that the book is useful to the speaker for learning Spanish. It does not mean to serve in the restaurant sense here.

Because servir is a stem-changing verb in the present tense: e → i.

Its present forms are:

• yo sirvo
• tú sirves
• él / ella / usted sirve

The subject here is Este libro, which is third person singular, so the correct form is sirve.

Me means to me or for me.

It shows who finds the book useful:

• Este libro sirve para aprender español = This book is useful for learning Spanish.
• Este libro me sirve para aprender español = This book is useful to me / for me for learning Spanish.

So me adds the idea of personal usefulness.

No. Here me is not reflexive.

It is an indirect object pronoun, showing the person affected or benefited: to me.

Compare:

• Este libro me sirve. = This book is useful to me.
• Me sirvo café. = I serve myself coffee.

That second example is reflexive-like servirse. Your sentence is not that.

In Spanish, object pronouns like me, te, le, nos usually go before a conjugated verb.

So:

• me sirve
• te sirve
• nos sirve

That is the normal position.

Because servir para is a very common structure in Spanish.

It means to be useful for or to be used to do something.

So:

• servir para + infinitive
• servir para + noun

Examples:

• Este libro sirve para aprender español.
• Esta herramienta sirve para cortar pan.

Using para shows the purpose.

After para, Spanish often uses the infinitive when talking about purpose in a general way.

So:

• para aprender español = in order to learn Spanish

You do not need a conjugated verb here.

A fuller structure is possible, but it is different:

• para que yo aprenda español

That means so that I learn Spanish, and it is less natural in this sentence.

Because este means this, and it must agree with libro.

Since libro is:

• masculine
• singular

the correct form is este.

Agreement chart:

• este libro
• esta mesa
• estos libros
• estas mesas

Because esto cannot go directly before a noun.

• este = demonstrative adjective before a masculine singular noun
• esto = neuter pronoun, used by itself

So:

• este libro = correct
• esto libro = incorrect

You can say esto on its own, for example:

• ¿Qué es esto? = What is this?

Because este already acts as the determiner.

In Spanish, demonstratives like este, ese, aquel normally replace the article.

So you say:

• este libro

not:

• el este libro

Because names of languages usually appear without an article after verbs like:

• aprender
• hablar
• estudiar
• enseñar

So:

• aprender español
• hablar inglés
• estudiar francés

That is the normal pattern.

In Spanish, names of languages are normally not capitalized.

So:

• español
• inglés
• francés

This is different from English, where you write Spanish, English, French with capital letters.

Yes.

• Este libro sirve para aprender español.
• Este libro me sirve para aprender español.

Both are correct.

The version with me is more personal: it says the book is useful to me specifically.

Without me, it sounds more general.

Yes, and it sounds natural.

There is a small difference in nuance:

• me sirve para aprender español = it is useful for that purpose
• me ayuda a aprender español = it helps me learn Spanish

Both work, but servir para focuses more on usefulness or function.

Yes, but the sentence as written is the most neutral and standard:

• Este libro me sirve para aprender español.

Other orders are possible in some contexts, but they usually add emphasis or sound less neutral.

For most learners, the best version to use is the original one.