This is the 685th most frequent Azerbaijani word.
olmasını
"Olmasını" means "its being" or "for it to be" in English.
Here, 'olmasını' is used to express the desire for a specific state (being happy) of the subject.
Onun xoşbəxt olmasını istəyirəm.
I want her to be happy.
In this sentence, 'olmasını' conveys the expectation for the book to possess a quality (being interesting).
Kitabın maraqlı olmasını gözləyirdim.
I was expecting the book to be interesting.
In this example, 'olmasını' represents hope for the decision matching a characteristic (being right).