ベストセラー
ベストセラー · besutoseraa · JLPT N1 · noun
best-seller
📚🔥 ベスト (best) + セラー (seller): a book that sells best, so it's a best-seller.
Katakana loanword from English 'best seller'. ベスト and セラー are both pronounced as in English, so the Japanese word is the English term spelled out. Read it as besuto + sera-.