Was Lee Harvey Oswald Just a Bad Shot?

Three years ago James Reston Jr. published The Accidental Victim, arguing that Lee Harvey Oswald was actually trying to kill Texas Gov. John Connally, and hit JFK only by accident. Some of the evidence comes from items collected after Oswald was arrested:

A Secret Service officer named Mike Howard was dispatched to Oswald’s apartment. Howard found a little green address book, and on its 17th page under the heading “I WILL KILL” Oswald listed four men: an FBI agent named James Hosty; a right-wing general, Edwin Walker; and Vice President Richard Nixon. At the top of the list was the governor of Texas, John Connally. Through Connally’s name, Oswald had drawn a dagger, with blood drops dripping downward.

Oddly, this page was subsequently ripped out of the little green book. No one knows how it happened. Reston also argues that Oswald had plenty of reason to hate Connally (as head of the Navy Department he had refused Oswald's request to restore his honorable discharge from the Marines) and no reason to hate JFK. What's more, Oswald's wife repeatedly testified that that Connally was Oswald's target.

I've never heard this theory before, and Reston's book doesn't seem to have gotten much attention. But his conclusion is clear:

For 53 years, a cottage industry has developed over the motive for the Kennedy assassination. It had to be connected to the Mafia or the Russians or the Cubans or Oswald’s Marxist beliefs or Jack Ruby’s petty crimes in the Dallas underworld....[But] Oswald was no coldhearted professional assassin under orders. The real answer to the reasons he took aim are to be found in his frustrations and obsessions. And the real tragedy of Dallas lies in the accidental death of a president who just happened to be in the line of fire.

So what's the deal here? Is this a real thing? Or just more JFK assassination crankery? If nobody believes Reston's theory, I'd at least be curious to hear the debunking.