That is, at any rate, the most abbreviated version of the story. “The facts of the Ruby Ridge affair, when maximally compressed, make no sense,” Chris Jennings writes in “End of Days,” a riveting and thoroughly researched chronicle of the 11-day standoff that attempts both the decompression and sense-making that has long eluded accounts of the event. How did an unemployed man who’d committed a petty crime manage to summon a multimillion-dollar response from the U.S. government involving snipers, helicopters and commando teams?