Learn Italian: Questo libro è noioso, ma è molto importante. - This book is boring, but it is very important.

Italian has two main groups of adjectives. The first group has four endings (-o, -a, -i, -e) to match gender and number. Since libro is masculine singular, it takes noioso. The second group only has two endings: -e for singular and -i for plural. Words like importante belong to this second group, so they use the singular -e ending for both masculine and feminine nouns.

Why isn't there a word for "it" before the second è?

In Italian, you usually drop subject pronouns (like "I", "you", "he", "she", "it") because the verb itself tells you who or what is doing the action. The verb è means "is", so è molto importante perfectly translates to "it is very important" without needing an extra word for "it".

Does molto change its ending like an adjective?

Not in this sentence! Here, molto means "very" and is acting as an adverb describing how important the book is. Adverbs never change their endings. However, when molto means "a lot of" or "many" and describes a noun directly (like molti libri for "many books"), it acts as an adjective and does change to match.

Is Questo acting as an adjective here?