Just ran across this in an ad in
The American Prospect.
Historian David Kaiser has a book out this year,
The Road to Dallas, The Assassination of John F. Kennedy (Harvard University Press, 2008) that looks like an engaging read. [I read the excerpt.]

I recall growing up reading of the significance of the JFK assassination in that modern American history was marked by November 22, 1963—
before and
after this terrible date.
I can't grapple with the main thesis here that Oswald did not act alone, but rather simply recommend that readers check out the book's site; the book looks like a fascinating read. We'll see.