Microsoft co-founder Paul Allen has hit out at Bill Gates in a new memoir by the billionaire venture capitalist.

Allen accuses Gates of taking Microsoft shares from him during the early days at the software company, following Allen’s treatment for cancer. The allegations form part of a new book on Allen’s life, schedule to go on sale next month. “Idea Man: A Memoir by the Co-founder of Microsoft,” details Microsoft’s early history and the close relationship between Bill Gates and Paul Allen.

Vanity Fair published an early excerpt from the book on Wednesday. In it Allen describes when he first met Gates:

“I saw a gangly, freckle-faced eighth-grader edging his way into the crowd around the Teletype, all arms and legs and nervous energy. He had a scruffy-preppy look: pullover sweater, tan slacks, enormous saddle shoes. His blond hair went all over the place. You could tell three things about Bill Gates pretty quickly. He was really smart. He was really competitive; he wanted to show you how smart he was. And he was really, really persistent. After that first time, he kept coming back. Many times he and I would be the only ones there.”

The Wall Street Journal quotes Paul Allen’s spokesperson, David Postman as claiming the book is “a very balanced portrayal of their relationship. Paul clearly values the input and the ideas and energy of Bill Gates.” Microsoft Chairman Bill Gates commented on the book in a written statement to the publication. “While my recollection of many of these events may differ from Paul’s, I value his friendship and the important contributions he made to the world of technology and at Microsoft,” said Gates.

The book reportedly contains several references to meetings that Allen claims he organised and chaired. The WSJ claims people familiar with the meetings said it was Gates who made the visits. Allen also reflects back with some bitterness according to the WSJ, who have been sent an early draft of the book. Allen feels throughout that he did not receive enough credit for his work.

Whether the memoirs are 100% accurate or not, the book is likely to reveal an interesting behind the scenes look at the very early days of Microsoft. Allen also reveals why he left the company, in part due to a conversation he overheard between Bill Gates and Steve Ballmer. The pair had planned to dilute Allen’s equity in the company by issuing options to themselves and other shareholders. Allen apposed the plan and the pair backed down.

Allen’s book will be available on April 17.