The musician stunned fans by quitting the band in 2015, and later revealed that one of his reasons for no longer touring with the group was his desire to hunt UFOs.
DeLonge is now continuing his work researching alien life by publishing a book featuring interviews with scientists, engineers, intelligence officers and military officials about the subject, according to RollingStone.com.
The 41-year-old co-wrote Sekret MAChines: Gods with with Peter Levenda and the book will hit shelves on 7 March (17).
"It was Levenda's ability to frame an esoteric thesis that gave me the ammunition to speak clearly on the subject matter, and that got me in the door," he says.
Sekret MAChines: Gods will be the first non-fiction book published by DeLonge. It will be a part of his To the Stars multi-media project.