RECOMMENDED There have been other respected critical studies of horror films, but Jason Zinoman has just written the most essential one we&rsquo;ve seen yet. In &ldquo;Shock Value,&rdquo; Zinoman, a theater writer for &ldquo;The New York Times,&rdquo; aims his critical eye and his hard reporter&rsquo;s nose at the era of horror that gave us &ldquo;Halloween,&rdquo; &ldquo;The [...]