Yes, I am absolutely 100% positive it is real. I watched him sign 15 books for an event we did with his law firm, Bracewell & Giuliani (which is why I also have a white ribbon with his law firm's name emossed on it). Three of the books were not used at the event and he gave them to me. I couldn't find an image of that page on the internet without the autograph, but I did find an autographed copy on eBay. As you can see that seller has a perfect rating, so it must have been authentic or they would have received bad feedback. http://www.ebay.com/itm/Leadership-Autographed-Author-Rudolph-Giuliani-/110664665890
The point is, the books are not printed with his autograph. He autographed them.