This is the 8818th most frequent Russian word.
популярная
Popular.
The word 'популярная' in this sentence is used to describe the book's status in terms of public favor during a specific timeframe.
Эта книга была самой популярной в прошлом году.
This book was the most popular last year.
Here, 'популярная' is used to characterize the idea as widely accepted or appealing among many people.
Популярная идея может изменить общественное мнение.
A popular idea can change public opinion.
In this case, 'популярной' (in the instrumental case) describes the person's growth in public appeal or recognition due to specific attributes or actions.