Long thought to be cordial but definitely not the best of friends, Microsoft co-founder Paul Allen dropped a few jaws today when he came out swinging against legendary co-founder Bill Gates.

But why now? Allen's upcoming memoir Idea Man is scheduled for publication in early April and excerpts are already starting to hit the Internet. At first, the observations are interesting and even a tad awe-struck as Allen describes the young Gates.

Bill came from a family that was prominent even by Lakeside standards; his father later served as president of the state bar association. I remember the first time I went to Bill’s big house, a block or so above Lake Washington, feeling a little awed. His parents subscribed to Fortune, and Bill read it religiously. One day he showed me the magazine’s special annual issue and asked me, “What do you think it’s like to run a Fortune 500 company?” I said I had no idea. And Bill said, “Maybe we’ll have our own company someday.” He was 13 years old and already a budding entrepreneur.

But the memoir is not a rosy romp through the early days of tech. Allen alleges that Gates schemed with #3 Steve Ballmer to dilute Allen's equity stake by issuing more options to others -- a plan foiled when Allen allegedly burst into the room and confronted them head on -- and that following his initial battle with Hodgkins disease, Gates used his absences to claim credit for many of his innovations. “I had helped start the company and was still an active member of management, though limited by my illness, and now my partner and my colleague were scheming to rip me off,” he claims. “It was mercenary opportunism, plain and simple.” Gates so far has only issued a vague and supportive statement of the book. Other Microsoft employees working at the time claim the Allen is wrong on many meetings and recollections. Sadly, most legendary pairings are not always the made for TV image we like to think, but it is sad to see another historical duo in such a petty light. Read the Excerpt on Vanity Fair Here