Harold Lloyd, the early screen comedian, took comedy seriously. ''I am not funny. Situations are funny,'' he is quoted as having said. ''Gags are funny . . . .'' When Lloyd put gag and story line together in his films, there was no doubt that the result would be sure-fire box office success.Today Lloyd should rank alongside Chaplin and Keaton, but most of the public has forgotten him. Why? Because by the depression audiences were less willing than before to identify with the comedian's Horatio Alger character, and his popularity ebbed. Later it was Lloyd himself who kept his old films off TV.With candor, Tom Dardis critiques the long list of Lloyd movies, also showing us the personal Lloyd in tantalizing glimpses that run like speeded-up sequences of an old flick. We see the actor as a workaholic, hobbyist, tightwad, and man of few friends. I found myself wanting to know more about his complex family relationships, his lonely wife.The most intimate views of Lloyd are at Greenacres, the comedian's palatial estate and self-monument. The author tapped the actor's family for personal reminiscences, but it will remain for others to write about Lloyd's personal side in depth. Until then, we have Dardis's excellent camera-eye view of the celluloid Lloyd.