Book on Nogtails

"Good gracious, it's getting dark already! I didn't notice that they'd lit the lamps! You'd better go and change into your robes, all of you. McLaggen, you must drop by and borrow that book on nogtails."

- Horace Slughorn dismisses the Slug Club from Compartment C.

A book on Nogtails was published at some point before September, 1996. During the first Slug Club meeting on 1 September, 1996, aboard the Hogwarts Express, Cormac McLaggen told Horace Slughorn about this book, and the latter asked him to lend it to him some day.

Appearances
Harry Potter and the Half-Blood Prince