This is the 15204th most frequent Russian word.
понравятся
"Понравятся" means "will be liked" in English.
In this conditional sentence, 'понравятся' is again future tense and plural, indicating that the liking is hypothetical contingent on future discovery or experience.
Если они тебе понравятся, мы их купим.
If you like them, we will buy them.
The word 'понравятся' is used here in the future tense, plural, meaning 'will like.' It implies that the second person singular ('you') will find these books appealing.
Эти книги понравятся тебе.
You will like these books.
Here, 'понравятся' expresses the hope that the gifts will be pleasing to the person(s), used in the plural and formal second person ('you').