A bestseller is a book that sells more copies than average. This is a purely quantitative characteristic that says nothing about the literary quality of the content.
In addition, a newly published book can be made known quickly through good marketing, which can be beneficial to sales figures. Already-published authors who actively promote their book on social media also ensure that sales figures increase.
Nevertheless, bestseller lists are very popular internationally. In Germany, the Spiegel bestseller lists are particularly well known:
SPIEGEL bestseller lists
Children's book recommendations can be found on the Stiftung Lesen website. For music and movies, visit the JPC website.