According to Conservapedia's article on William Ayers:
In an October 2008 article in American Thinker, Jack Cashill presented evidence that Ayers ghostwrote Obama's first book, "Dreams From My Father". He based his assertion on a comparison of the writing styles of Bill Ayers' 2001 memoir, Fugitive Days, and Barack Obama's earlier 1995 book, Dreams From My Father, and came to the conclusion that Ayres had ghostwritten Dreams.
In the Cashill article, Who Wrote Dreams From My Father?, Cashill states:
As shall be seen, however, there are only two real possibilities: one is that Obama experienced a near miraculous turnaround in his literary abilities; the second is that he had major editorial help, up to and including a ghostwriter.
Cashill then goes on to list the reasons why he believes Bill Ayers, ghost-wrote "Dreams":
I bought Bill Ayers' 2001 memoir, Fugitive Days, for reasons unrelated to this project. As I discovered, he writes surprisingly well and very much like "Obama." In fact, my first thought was that the two may have shared the same ghostwriter. Unlike Dreams, however, where the high style is intermittent, Fugitive Days is infused with the authorial voice in every sentence. What is more, when Ayers speaks, even off the cuff, he uses a cadence and vocabulary consistent with his memoir. One does not hear any of Dreams in Obama's casual speech.
Cashill then goes on to list a myriad of ways he believes that Obama and Ayers are connected socially, politically, and ideologically.
This is a guy who lives in my neighborhood, who's a professor of English in Chicago who I know and who I have not received some official endorsement from. He's not somebody who I exchange ideas from on a regular basis.
It would seem implied from this statement that Obama has not sought a close relationship with Ayers and thus it is unlikely that he ghost-wrote Obama's book.
Is there any truth or evidence to support Cashill's claim that Obama's book "Dreams From My Father" was written by Bill Ayers?