The Evans and Novak version of Reagan's route to the Presidency and his first hundred days has the advantage, as well as the handicap, of partisanship-- they're all for the so-called Reagan ""Revolution"" (a return to the US world position of 1955, to the domestic situation of 1925), so they've kept close tabs on its progress: their chapters on the Reagan candidacy chiefly detail who, purist or pragmatist, true right-wing Reaganite or mere centrist Republican, had his ear and trust at any given time; ditto, in terms largely of supply-siders and subversive Others, the early days of the new administration. So lots of the book is about Lynn Nofziger and Jeffrey Bell and John Sears, and their conflicting strategies (and the Jack Kemp-Jude Wanniski economic-policy input). Then, come the election, each of the Revolution's ""battlefronts""--tax reduction, budget-cutting, deregulation, anti-Sovietism--becomes intramural warfare. . . with only OMB director Stockman, Interior Secretary Watt, and the president's ""quiet"" assistant for domestic policy, Dr. Martin Anderson, deemed by Evans and Novak as ""radical"" as Reagan. (It was Anderson, we hear, who blocked the quota on Japanese car imports--but the compromise ""voluntary quota"" was still suspect as ""opening the door to pleas for help. . . by other distressed industries."") On Reagan himself, they're both candid and sly. Sure, he's no intellectual--but all that magazine reading doesn't only give him crackpot notions, it keeps him open to new ideas. It's no bad thing, either, that his favorite talk is about ""the old days in Hollywood,"" or that he had ""so bizarre a preparation for political office"": few recent presidents ""had so long a career in the private sector."" Mostly, though, he's the most rigidly ""ideological"" president since his hero, Calvin Coolidge. So why so few ""radicals"" around? ""He does not""--in the words of an associate--""perceive himself to be one."" Some transient intelligence, then, from the inside track.