enthusiast, fan, hobbyist
そして本の愛好家の間でも大変有名です
It is also very well known among book lovers.
— お嬢さん (2016)
推理小説愛好家のための特別な休日です。
It's a special holiday for mystery novel enthusiasts.
彼は熱烈な音楽愛好家だ。
He is a passionate music lover.