Surprisingly, one of the most literate documentary series around is Bravo's ''Page to Screen,'' which is about how books have been translated to film. In the program about John Irving's ''Cider House Rules,'' for example, Irving, who wrote the film's screenplay, describes the novel's ''moral symmetry'' as making it particularly suitable for film adaptation and discusses the need to cut certain characters and tone down the flaws in others because extremes that work well in print can overwhelm on the screen. That's the kind of nuts-and-bolts formal analysis that even the best author interviews tend to bypass. But don't get too excited about ''Page to Screen.'' It's been canceled.