The Gaku Gaku no Mi is a Paramecia-type Devil Fruit that allows the consumer to absorb knowledge through touch.
The main strength of the fruit is the fact that the person can absorb any form of information just by touching the source of it. This includes books as well as people, so it is a useful interrogation tool without having to go through the hassle of questioning an individual. Its powers offer indefinite absorption, so the user can even absorb techniques and unique fighting styles.
The fruit has no known weaknesses outside of the standard Devil Fruit weakness.