Ho scelto quel libro per la copertina rossa, ma l’autrice mi ha convinto per la sua chiarezza.

They are both in the passato prossimo, a very common Italian past tense used for completed actions.

• ho scelto = I chose / I have chosen
• ha convinto = she convinced / has convinced

The structure is:

• avere in the present + past participle

So:

• ho
  • scelto
• ha
  • convinto

Italian uses this tense very often where English might use either the simple past or the present perfect.

Quel is the form of quello used before most singular masculine nouns beginning with a consonant.

So:

• quel libro
• quel ragazzo
• quel tavolo

But Italian changes the form in some cases:

• quello studente
• quello zaino
• quell’amico

This works a lot like the definite article system:

• il libro → quel libro
• lo studente → quello studente
• l’amico → quell’amico

In this sentence, per means something like because of, for the sake of, or on the basis of.

So:

• Ho scelto quel libro per la copertina rossa
  = I chose that book because of the red cover.

• l’autrice mi ha convinto per la sua chiarezza
  = the author convinced me because of her clarity.

This is not the same as per meaning only for in the sense of destination or purpose. Here it expresses the reason behind the choice or reaction.

Because copertina is a feminine singular noun, and the adjective rossa has to agree with it.

• copertina = feminine singular
• therefore la
• and rossa also feminine singular

Compare:

• il libro rosso
• la copertina rossa
• i libri rossi
• le copertine rosse

So this is a basic case of noun-adjective agreement.

Because autrice begins with a vowel, and la becomes l’ before a vowel sound.

• la autrice → l’autrice

This is called elision.

You see the same thing in:

• l’amica
• l’idea
• l’ora

Yes. Autrice is the feminine form meaning female author.

• autore = male author / author in the masculine form
• autrice = female author

You may sometimes also encounter women referred to as autore in some contexts, but autrice is absolutely a standard and widely used feminine form in contemporary Italian.

Mi means me.

So:

• l’autrice mi ha convinto = the author convinced me

It is a direct object pronoun placed before the auxiliary verb.

Compare:

• L’autrice ha convinto me = less neutral, more emphatic
• L’autrice mi ha convinto = normal word order

Italian object pronouns usually come before the conjugated verb or auxiliary:

• mi ha visto = she saw me
• ti conosco = I know you
• ci hanno chiamato = they called us

It can, but mi ha convinto is the normal, unmarked way.

Italian usually prefers short object pronouns before the verb:

• mi = me
• ti = you
• lo / la = him/it, her/it
• ci = us
• vi = you plural
• li / le = them

Using the full form me after the verb gives extra emphasis, something like:

• ha convinto me, non te
  = she convinced me, not you

So in your sentence, mi ha convinto is the most natural choice.

In Italian, possessive adjectives usually go with a definite article.

So:

• la sua chiarezza
• il suo libro
• la mia idea
• i nostri amici

That is why Italian does not usually say just sua chiarezza.

A common exception is with many singular family words:

• mia madre
• tuo fratello
• suo padre

But chiarezza is not one of those exceptions, so the article stays.

Grammatically, sua can mean his, her, or its. Italian possessives agree with the thing possessed, not with the possessor.

Here:

• chiarezza is feminine singular
• so the possessive is sua

To know whether it means his, her, or its, you look at the context. In this sentence, it clearly refers to l’autrice, so it means her.

Because Italian often omits subject pronouns when they are clear from the verb form.

• ho scelto already tells you the subject is I
• ha convinto with l’autrice explicitly named tells you who did the action

Italian is a pro-drop language, so subject pronouns like io, tu, lui, lei are often unnecessary unless you want emphasis or contrast.

For example:

• Io ho scelto quel libro, ma tu no
  adds contrast
• Ho scelto quel libro
  is the normal neutral form

Because with avere, the past participle usually does not agree with the subject.

So even if the speaker were female, you would still normally say:

• ho scelto
• ha convinto

This is different from verbs that use essere, where agreement with the subject is required:

• Maria è andata
• Luca è andato

With avere, the participle usually stays in its default form unless special agreement patterns come into play, especially with certain preceding direct object pronouns.

Yes, exactly. That is one of the main effects of ma here.

The sentence contrasts:

• the superficial or first reason: the red cover
• the deeper or more meaningful reason: the author’s clarity

So the structure is roughly:

• I picked the book because of its cover, but I was won over by the author’s clarity.

This kind of contrast is very natural in Italian, and repeating per helps make the parallel structure clear.