korien_april17“How was the concert?” 「コンサートどうだった?」
“It was okay. Nothing to write home about.” 「まあまあ。実家に手紙を送るほどでもない。」


The idea of this idiom is that if something incredible and amazing happened, you would write home to tell your family about it. For example, if you saw a movie or concert or read a book and really liked it, you would send a letter (or perhaps an email) to your parents to tell them how great it was. But the concert was just okay, nothing special, so you don’t have to write home.