Learn Spanish (Latin America): Mis amigos leen libros interesantes.

Leen comes from the regular -er verb leer (to read). Since the subject is mis amigos (my friends, which is the "they" form), you drop the -er ending and add -en.

How do I pronounce the double 'e' in leen?

You don't pronounce it like the English word "lean". In Spanish, you generally pronounce every vowel. So, you say both 'e' sounds one after the other, sounding like "leh-en".

Why are the words flipped to libros interesantes instead of "interesting books"?

In English, descriptive words (adjectives) go before the noun. In Spanish, they usually go after the noun they describe. So, you literally say "books interesting".

Libros is masculine. Why isn't the adjective interesantos?

Adjectives that end in -e in their base form (like interesante) are gender-neutral. They use the same form for both masculine and feminine nouns. Since libros is plural, you simply add an -s to make it interesantes.

Why is it mis amigos instead of ?