NEW YORK — Author of "The 48 Laws of Power," Robert Greene, says hanging out with 50 Cent while writing the new book "The 50th Law" was fun and amazingly eye-opening.

"He was a real pleasure to work with," Greene said Thursday (September 10) at the 46th Street Barnes & Noble in Manhattan. "It was kind of shocking. We met a few years ago. We had a nice vibe together. We felt like we kind of think alike. He was so easy to work with. I think he trusted me because he likes 'The 48 Laws of Power.' The only thing was, I was bothering him a lot to get more access to him, talk to him more."

"It was exciting for me," Fif said. "Me and Robert, we started on this project ... we met in 2006. For a while, we've been compiling information to create it. I thought 'The 48 Laws of Power,' the cool thing about it was the research. A lot of people that read it only enjoyed the short — it directly related to the environment they were growing up in. To see the comparison to people from previous times in history that utilized those same rules in situations that I wasn't aware of is what made me exited about the book."

Green says as eye-opening part of the experience was seeing 50's business side.

""I saw some weird stuff going down in his office," Greene laughed. "Fist fights happening in his office at G-Unit clothes. The whole fake thing he did about throwing that plasma TV off the wall, creating a story outta nothing."

Fif says that book signings are tamer than album signings, but some fans showed him some audible love.

"I'm about to have a hot flash," one girl said after 50 signed her book. There were also a few guys singing "187" from Fif's new song "Flight 187." 50 smiled and nodded in approval.