From Scarface to Scarlett, by Roger Dooley. New York: Harcourt Brace Jovanovich. 648 pp. $25. As decades go, the 1930s are easy to mark off. In life, they began with the crash and ended with World War II. At the movies, they began with the triumph of talkies, and ended with the unsurpassed glories of 1939 - a year that gave us exactly 365 Hollywood productions, including such titles as ''Gone With the Wind ,'' ''The Wizard of Oz,'' ''Stagecoach,'' ''Ninotchka,'' ''Wuthering Heights,'' ''Mr. Smith Goes to Washington,'' and even ''Gunga Din.'' Not bad for a 12-month stretch, which has been called the high point as well as the midpoint of the screen's ''golden age.''
In his massive new book, English professor and film buff Roger Dooley does his best to chronicle the entire output of Hollywood during the '30s, basing his survey on research into all the American features - almost 5,000 - reviewed then by the New York Times and Film Daily, leaving out only B westerns that never played first-run theaters. The result is a rousing and readable history of movies, mores, and memories.
Since people flocked to films in the '30s - with scores to hundreds of pictures available each week in every American city - it seems fair to conclude that movies reflected current attitudes and ideas. Dooley sums these up in neat observations that he supports with titles and plot synopses. We learn that moviemakers ''loved their doctors, distrusted their lawyers and had all but forgotten their teachers.'' And we encounter unwritten rules of the screenwriting game, some less attractive than others. In triangle dramas, ''the husband and wife always ended together,'' no matter how many plot twists were required. Less appealingly, ''when two young people of different races fell in love,'' the wages of this ''sin against ethnic purity'' was inevitably ''death for at least one, preferably the one with darker skin'' - unless he or she turned out to be actually white, in which case all was forgiven.
Many of these rules were codified in the Motion Picture Production Code of 1934, which became a watershed between the looser, more liberated films of the early '30s and their euphemistic, somewhat uptight successors. The results of the code were not all negative, as Dooley notes, recalling that movies resourcefully sought methods and mannerisms that could be ''far wittier than latter-day sexual explicitness.'' But the code had its dark side, too, in matters of self-righteousness and social prejudice masquerading as morality. Along with comical clergymen and ''illegal weapons in the hands of gangsters,'' for example, miscegenation was also forbidden - a stricture that sadly suited a decade in which only three films took their black characters seriously, and when Chinese characters were treated almost as deplorably as American Indians and blacks. Then too, remember all the comedies and dramas ''which under the guise of inspiring patriotism actually glorified militarism,'' full of Yankee Doodle Dandies who ''managed aggressively to protect American 'interests' from mere natives.''
For the rest, it was a decade of odd contradictions between real life and movie life. Families in films rarely had financial troubles even though a depression was raging away; gangsters became folk heroes on the silver screen; a largely Protestant country and a mostly Jewish studio establishment churned out film after film about feisty Irish priests. And audiences cherished their favorite pictures without the slightest notion they would be remembered by future generations, much less studied as cinematic art.
As for the movies themselves, Dooley captures them hurriedly but effectively, organizing them into 50 categories ranging from ''Love Among the Millionaires'' to ''Films of Ideas.'' Chapters have such headings as ''Backstage Musicals,'' ''News Hawks and Sob Sisters,'' and ''Our Fettered Friends'' - jailbirds, that is - spiced with quotes like ''Each time you go up there . . .'' and ''If love were all,'' not forgetting the ever-popular ''I'm bustin' out!'' It's enough to make a movie fan say, ''We can't go on this way'' or ''Ah . . . give the kid a break!'' Except it's too much fun. This is a star-struck, scholarly, and eminently cinematic book.