Learn Polish: Będę czytać długie listy i nowe książki. - I will be reading long letters and new books.

To talk about an ongoing action in the future ("will be reading"), you use the future form of "to be" (będę) followed by the infinitive of a verb like czytać. You can also use the past tense form instead of the infinitive (będę czytał or będę czytała), and it means the exact same thing!

Why are the words for letters and books in the accusative case here?

The verb czytać (to read) needs a direct object. In Polish, the direct object—the thing being acted upon—takes the accusative case. Since you are reading multiple letters and books, we use the accusative plural.

List is masculine and książka is feminine. Why do their adjectives (długie, nowe) both end the exact same way here?

In the plural, Polish simplifies genders into just two groups: "virile" (groups with at least one man) and "non-virile" (everything else, including objects like letters and books). Because both are non-virile, their adjectives share the same non-virile accusative plural ending, which is -e.

The singular for book is książka. Why does the plural end in -i (książki) instead of -y?