“This book became popular because it really struck a chord with its audience.”
If something “strikes a chord” with you it means that it touches on a meaningful subject in a way that you can relate to. You could also say it “speaks to you”.
「この小説は読者の共感を呼んで人気が出ました。」
何かが strikes a chord （弦を打つ）は、意味のある話題について共感できるメッセージを伝えるということです。speaks to you（自分に話す）とも言います。
