One Piece, Vol. 31 continues where the previous tankōbon left off and contains the next ten chapters (286–295) of the on-going manga series.
This tankōbon continues the Skypiea Arc. In a flashback, Montblanc Noland, Cricket's ancestor, arrives on Jaya. He finds the early Shandians, who are being plagued by a terrible disease. After curing them a friendship is formed and although Noland is forced to return to his homeland, the Shandians promise to help them meet again by ringing a special golden bell. Soon afterwards Skypiea is launched into the sky, and the inhabitants of Angel Island expel the Shandians from Skypiea.
Meanwhile, in the present, the Shandians continue to fight to reclaim the bell that will reunite them with Noland, not knowing he has long since been executed for "lying" about Skypiea's location. Wishing to ring the bell to let Cricket know that Skypiea exists, Monkey D. Luffy unites all the people of the sky against Eneru.
This tankōbon is written and illustrated by Eiichirō Oda. For the most part, it is written and illustrated rather well. Most of the tankōbon focuses on the history of Skypiea and how it came to be, which reflects on the plan to win this civil war in the sky by Monkey D. Luffy.
All in all, One Piece, Vol. 31 is a wonderful continuation to a series that seems really intriguing and I can't wait to read more.