Question: Hey, Odacchi! I got a question! About Devil Fruits!! If Kaku and Kalifa said they wouldn’t know what their Devil Fruit were until they ate it, how come Shanks knew what Luffy’s Gomu Gomu no Mi was before he ate it?? Tell me! Tell me now!! Pleeeease tell me!!! P.N. Shirogitsunekko
Oda: Well, I think I’ll eventually get to explaining more about Devil Fruits in the main story, but you see, there’s a book of Devil Fruits.
It has info about all kinds of fruit names and abilities, but few of the fruit can actually be identified by their shape. In the case of the Gomu Gomu no Mi, there was a picture and everything, but for Kaku and Kalifa, they were talking about how they wouldn’t know until they had finally eaten the fruit. The Volume 45 SBS is over!! Until next time!!
This would imply that the information in the book is incomplete since only a few of devil fruits have illustrations (meaning that most Devil Fruits cannot be identified by their appearance) and that there are still devil fruits out there with attributes that have yet to be documented.
One individual known to utilize this book is Blackbeard, who, in his search for the Yami Yami no Mi, memorized its shape from the illustration provided. The Vinsmoke Family also has a copy of the encyclopedia, which Sanji read and became interested in the Suke Suke no Mi.