that's one for the (record) book(s)

that's one for the (record) book(s)

That is a remarkable, unusual, or unexpected event, occurrence, or piece of news. Mr. Literature Snob reading a trashy romance novel? Now that's one for the books! A: "After the concert, I ran into the singer at a pub down the road from the venue. It turns out, his mother went to the same school as mine!" B: "Wow, that's one for the record book!"
See also: one