​Bestselling author John Green and his online-video entrepreneur sibling Hank Green are stopping at the University of Montana for a tour supporting John's new novel, "Turtles All the Way Down."

At the event, the two will discuss the book, answer questions, play some music and more, according to a news release from Shakespeare & Co. bookstore.

The event is at 7 p.m. Friday, Oct. 27, at the Urey Underground Lecture Hall on the UM campus.

Tickets are $23.50, on sale now at brownpapertickets.com/event/3083401. Each ticket includes a signed copy of the book. Only two tickets are allowed per person.

The news release warns that ​"a ticket must be present for entry. No ticket, no entry, no exceptions."

John is best known for "The Fault in Our Stars," a 2012 novel that covers teenage romance and terminal illness, which won him legions of adult and young-adult fans.

"Turtles" will be released on Oct. 10. According to the summary on his website, the novel is about "Sixteen-year-old Aza (who) never intended to pursue the mystery of fugitive billionaire Russell Pickett, but there’s a hundred-thousand-dollar reward at stake and her Best and Most Fearless Friend, Daisy, is eager to investigate. So together, they navigate the short distance and broad divides that separate them from Russell Pickett’s son, Davis.

"Aza is trying. She is trying to be a good daughter, a good friend, a good student, and maybe even a good detective, while also living within the ever-tightening spiral of her own thoughts."

The two are known as the Vlogbrothers, a YouTube channel they started together over 10 years ago to stay in touch while living in separate parts of the country; Hank is based in Missoula. They quickly expanded into multiple channels, such as "Crash Course" and "SciShow." Hank also co-founded VidCon, the annual video-blogging conference that is expanding with international events.