Learn Italian: Ho trovato un libro interessante da leggere.

In Italian, when you want to express the purpose of a noun or what needs to be done with it, you use the preposition da directly before an infinitive verb. So, un libro da leggere means a book meant to be read. You will see this pattern often with nouns and pronouns, such as in qualcosa da bere (something to drink).

Libro is masculine, so why does interessante end in -e instead of -o?

Not all adjectives end in -o or -a. Adjectives that end in -e in their dictionary form, like interessante or grande, are used for both masculine and feminine singular nouns. They only change their ending to -i when they become plural.

Why does interessante come after libro rather than before it?

Unlike English, Italian generally places descriptive adjectives after the noun they modify. Since interessante describes a specific quality of the book, it naturally goes right after libro.

Why does trovato end in -o? Does it need to agree with libro?