It's hard to pinpoint the one book that has been the most popular in 2020. Every individual's tastes vary and the popularity of a book depends highly on the opinion of its readers. This makes it difficult to name one book as the "number one book of the year."
That being said, some of the most talked about and acclaimed books of the year have been "The Testaments," the sequel to Margaret Atwood's award-winning "The Handmaid's Tale," and "Where the Crawdads Sing," by Delia Owens. Both books have been widely praised and have become some of the most recognizable books of 2020.
Of course, there are many other books of the year worth mentioning such as "Know My Name" by Chanel Miller, "Mexican Gothic" by Silvia Moreno-Garcia, and "The Vanishing Half" by Brit Bennett, just to name a few. With so many amazing books being released in 2020, the competition has certainly been tough.
In the end, the best book of 2020 will likely remain subjective and up to personal opinion. Whether you read one book or twenty books this year, the important thing is to find books that speak to you and that you enjoy.