Learn Hardcore Italian: Anna legge un libro interessante.

Because Anna is a single third-person subject (she), so the correct conjugation of leggere in the present tense is legge (she reads). If you were talking about yourself (I read), you would say leggo, or if you were talking about multiple people (they read), it would be leggono.

What is the meaning of un in un libro interessante?

Un means "a" or "one" and is the indefinite article used in front of masculine nouns that start with most consonants or vowels. So you say un libro because libro is a masculine noun starting with a consonant. If the noun were feminine or started with certain consonant clusters, the article might change (e.g., una casa, uno studente, un’amica).

Why does interessante come after libro?

In Italian, adjectives commonly follow the noun they describe. While some adjectives can come before or after the noun (and sometimes this can slightly change the meaning or emphasis), the normal pattern is noun + adjective. So it’s perfectly standard to say un libro interessante instead of un interessante libro.

Is interessante describing the book or Anna?