This is the 8771st most frequent Swedish word.
bästsäljare
"Best seller."
The word 'bästsäljare' in this sentence is used as a noun to describe a book that sells extremely well and is popular among readers.
Den här boken är en bästsäljare i Sverige.
This book is a bestseller in Sweden.
In this example, 'bästsäljare' refers to the quality of becoming highly popular and well-sold, highlighting the success of the referenced object.
Att det blev en sådan bästsäljare förvånade ingen.
That it became such a bestseller surprised no one.
Here, 'bästsäljare' is used in a descriptive function emphasizing the status and recognition of her novel in the market.