The beauty of a book like Case Closed is that it claims to have all of the answers. If the reader is willing to blindly accept everything the author states as fact, they may be left feeling as if they know the answer to the great American murder mystery. There's no doubt that Posner is a strong, if simplistic, writer and as a former lawyer he knows how to present a case. And he most certainly has his lawyer hat on when he presents what basically amounts to a prosecutors brief. He cherry-picks the evidence, choosing only the witness testimonies and statements that support his arguments whilst ignoring and misrepresenting those that do not. Worst of all, when there is no evidence to support one of his claims, he says there is anyway!
Case Closed is rife with factual errors. In fact there are probably more inaccuracies in this book than in any of the hundreds of pro-conspiracy books that Posner spends half of his time criticising. For example:
p255: Posner claims that railroad workers on the overpass could not have seen puffs of smoke from rifle fire on the knoll "since modern ammunition is smokeless, it seldom creates even a wisp of smoke." This is provably false. Even a government investigation of the assassination refuted this. (see HSCA report p606)
p13n: Posner cites the reports of two Soviet psychiatrists claiming that they support the notion that Oswald was mentally unsound. They do not. (see Warren Commission hearings vol. 18 p464-73)
p257: Posner claims that eyewitness Ed Hoffman could not have seen a gunman behind the picket fence atop the grassy knoll because his view was blocked by "four large railway freight cars." All known films and photos show this to be false.
p329: According to Posner the exact moment Governor Connally was hit can be pin-pointed at frame 224 of the Zapruder film because "the right front of the Governor's suit lapel flips up from his chest." He neglects to mention that the bullet hole in Connally's jacket was several inches down from the lapel in the jacket body beneath the right nipple area.
And so on.
This is not to say that Case Closed is entirely without merit. Regardless of whether or not you agree with the author's conclusions, it is a very enjoyable read. Even though I know it is woefully biased and inaccurate I was gripped by Posner's biography of Oswald. And he does debunk a few of the sillier theories on the assassination (such as the bizarre body alteration theory put forth in David Lifton's book "Best Evidence"). Still, it's probably best to treat this book as what it is; a work of fiction.