IT IS a pleasure -- particularly in this era of revisionist historians, psychohistorians, muckrakers, and investigative reporters--to come across an author who likes his subject. Not only that, but he writes a clear, concise and well-documented story from beginning to end.

This is not to say Nathan Miller hands us a completely uncritical biography. Still, it is certainly a favorable one about a remarkable man whom the historians generally classify as either our first- or our second-ranked president, after Lincoln.

Nathan Miller has been a Washington journalist by trade, which may well account for his clean and felicitous writing. He spent many years at The Baltimore Sun; he has also been a staff man on the Hill and worked in the executive branch of the government. His previous writings indicate he is something of a naval expert, as of course was Roosevelt.

FDR: An Intimate History is a book for the young who never knew this man of irresistible charm and magic, which were on display for so many years in Washington and, for that matter, the nation and the world. But it is also for the nostalgic old who came under the spell of FDR in their youth and who would like once again to recall those sparkling days and glamorous battles. His four-term presidency, filled always with action, was of course the longest in our history.

Still, three-fifths of the book has passed before Roosevelt gets to the White House. It begins with his birth at Hyde Park to a formidable but doting mother and a much older father who died when Roosevelt was a child. He led from the beginning a socially secure and protected life of wealth.

Roosevelt went to Groton, the snobbish Episcopalian Massachusetts prep school, leavened by a remarkable headmaster, Endicott Peabody, who ingrained in young Franklin and all his other students a remarkable sense of duty owed to the nation. He then went to Harvard where he was president of the Crimson, the daily newspaper, and he later went to Columbia Law School--not Harvard--because he could see occasionally in New York Eleanor Roosevelt, whom he married while in law school. He then tried the law, but it bored him and he really did not need to make a living.

Politics and government soon wholly absorbed him. He ran for the state senate, campaigning in a red touring car that scared the local horses. He proved so adept he defeated the Republicans in Duchess County, a feat he was able to repeat only once in the four times he ran for president. Even early he was a superb campaigner and he quickly drew state and national attention by taking on and beating Tammany Hall in the legislature. As a prot,eg,e of the anti-Tammany Woodrow Wilson, he came to Washington as assistant secretary of the Navy, imitating his Republican cousin, Theodore Roosevelt.

Although FDR talked often to his contemporaries about eventually running for president he did not carefully plan his career. But everything he ever did contributed to his training for the job. He spent eight years in Washington as assistant secretary of the Navy, both in peacetime and in wartime. By the time he left, there was little if anything he did not know and understand about how Washington ran. Exactly the same point about training could be made of his two terms as governor of New York--the largest and most powerful governorship in the nation.

He had also already campaigned around the country as the Democratic nominee for the vice presidency in 1920, although he was only 38. He was beaten in that election as he had earlier been beaten when he tried to get the Democratic nomination for United States senator from New York. But he made lifetime political friends all over the country who were to stand him in good stead only 12 years later when he first ran for the presidency.

Miller is fascinated by and friendly to Roosevelt, but he does discuss all the famous criticisims, such as his supposed deviousness, and his difficulty in making up his mind at certain times. He discusses succinctly the FDR romance with Lucy Mercer, his wife's social secretary. There is a comprehensive and excellent summary of all the New Deal battles, the many victories and the few defeats. And the author makes deft use of anecdotes throughout to illustrate and strengthen his points.

There are, to be sure, some criticisms to be made of Miller and his treatment of FDR. There are some nitpicking errors--for an example, the redoubtable Ben Cohen, the famous New Deal draftsman, was indeed a young friend of Justice Brandeis, but he was never his law clerk.

This reviewer finds rather puzzling his skimpy treatment of Roosevelt as the World War II leader. After all, this is probably FDR's most important accomplishment, even including his leadership of the New Deal against the Depression. He allows only 30 pages for the period from Pearl Harbor to Roosevelt's death just before World War II ended. Yet he has given the eight-year period as assistant secretary of the Navy 80 pages. This difference in scale is perplexing. After all, a Navy buff like Miller could have written about the greatest fleets and greatest sea battles ever seen.

Even this is minor criticism. He has brought Roosevelt to life once again throughout the entire book.