La bibliotecaria me recomendó una novela corta que trata de una chica que quiere mudarse sola.

Bibliotecaria means female librarian. In Spanish, many job titles change form depending on the person's gender:

• el bibliotecario = the male librarian
• la bibliotecaria = the female librarian

Here, the sentence is talking about a woman, so it uses la bibliotecaria.

Me is an indirect object pronoun meaning to me.

So:

• La bibliotecaria recomendó una novela = The librarian recommended a novel
• La bibliotecaria me recomendó una novela = The librarian recommended a novel to me

In Spanish, this pronoun usually comes before the conjugated verb:

• me recomendó
• te recomendó
• le recomendó

Even though English often uses to me, Spanish normally uses just me here.

The accent mark shows that this is the preterite form, third person singular:

• yo recomendé = I recommended
• él/ella/usted recomendó = he/she/you recommended

So recomendó means recommended.

Without the accent, recomendo would not be the correct standard form here.

In Spanish, adjectives often come after the noun, especially when they describe a factual quality:

• una novela corta = a short novel

Also, novela corta is a very common combination and can even mean novella, not just any novel that happens to be short.

If you said una corta novela, it would sound less natural in most everyday contexts.

Tratar de here means to be about or to deal with.

So:

• una novela corta que trata de una chica... = a short novel that is about a girl...

This is a very common way to describe the subject of a book, film, or story.

For example:

• Es una película que trata de la guerra. = It’s a film about war.

Both ques are relative pronouns, meaning that / who in English.

The sentence has two linked descriptions:

• una novela corta que trata de una chica = a short novel that is about a girl

• una chica que quiere mudarse sola = a girl who wants to move out on her own

So each que introduces extra information about the noun before it.

Chica usually means girl or young woman, depending on context.

It is less specific than English sometimes expects. It can refer to:

• a girl
• a young woman
• sometimes simply a female person in an informal way

So una chica is a very natural choice in everyday Spanish.

Because mudarse is the usual verb for moving house / moving to a new place to live.

• mudar by itself often means to change or is used in more limited contexts
• mudarse means to move (oneself), to move home

So:

• quiere mudarse = she wants to move

This is a pronominal verb, which is why it includes -se.

When a pronominal verb follows a conjugated verb and stays in the infinitive, the pronoun can attach to the end.

Here:

• quiere mudarse

This is equivalent in structure to things like:

• voy a levantarme
• necesita ducharse
• prefiero sentarme

With infinitives, attaching the pronoun is normal and very common.

Sola means alone or by herself.

So:

• quiere mudarse sola = she wants to move on her own / by herself

It agrees with chica, which is feminine singular, so Spanish uses:

• solo for masculine
• sola for feminine

If the sentence were about a man, it would be:

• un chico que quiere mudarse solo

In this sentence, the most natural meaning is that she wants to move out and live by herself.

So mudarse sola usually suggests moving to her own place alone, not simply carrying boxes without help.

Context could change the nuance, but in a sentence about a girl and a novel plot, that is the interpretation most learners should assume.

Because the expression is tratar de when it means to be about.

So the structure is:

• tratar de + noun/topic
• trata de una chica
• trata del amor
• trata de la guerra

That de is required by the verb expression in this meaning.

Quiere is the present tense, third person singular, from querer:

• yo quiero
• tú quieres
• él/ella quiere

So una chica que quiere mudarse sola means a girl who wants to move out on her own.

Even though recomendó is in the past, the content of the novel is described in the present. This is very common in both Spanish and English when talking about plots or general content.