One Piece was a manga story that took place in the fictional world of pirates. It mainly told the adventure story of Luffy and others in search of the legendary treasure. Therefore, whether One Piece was suitable for adults over the age of 30 depended on their personal interests and reading preferences. If one was interested in the fictional world of pirates and liked adventure and pirate stories, One Piece might bring a good reading experience. However, if you don't like this type of story or think it's too long, it might not be suitable for reading. Whether reading was suitable or not depended on one's interests and reading habits. If you were interested, you might find One Piece to be a good book to read.