The secret society of biography buffs, a nonexistent organization to which I belong, sometimes meet in the corners of cocktail parties where the talk turns to which of the more recent ones concerning politics is the best. Is it "Huey Long" by T. Harry Williams? Is it "Shadow of Blooming Grove" by Francis Russell? Or is it "The Rise of Theodore Roosevelt" by Edmund Morris. Most of the time Morris wins hands down.

Morris has been chosen by President Reagan to be his biographer, and what a wonderful choice it is. The president has offered Morris access to White House staff meetings, to his papers, to a diary that he has been keeping, and to his very person. From time to time, the two of them will meet and Morris will be free to ask what he wants. The rules say the president is supposed to answer, although, as everyone knows, there is no stopping him from telling yet another story about his Hollywood days.

The newspapers say that Morris will get $3 million for his Reagan book. Anyone who has ever read his "The Rise of Theodore Roosevelt" will no doubt agree he is worth every penny. That book is one you finish in sadness. For as long as it lasts, and it lasts quite a long time, it becomes one of those books you live, rather than read, and the subsequent days are spent searching out people with whom to share the experience. My search for people with whom to share the book finally led me to Morris himself. As a man, he is as good as his book.

But alas, he appears to be something of a conservative. He and I avoid the subject of politics. He knows where I stand, and I know, or suspect, where he does. My only question is how a man of his evident intelligence and talent can be immune to the fruits of his own scholarship and remain on the right, rejecting what is obvious: truth and liberalism are one and the same thing. But I am forever disappointed in this. Francis Russell, whose biography of the libidinous and fascinatingly plain Warren Harding is a riveting classic, turns up on the masthead of the National Review. Daniel Boorstin, whose trilogy "The Americans" is as good a read as there is in history, is likewise a conservative. Why do my virgins turn out to be otherwise?

Although you could never tell from the writing, Morris was both stymied and frustrated by the lack of anectodal material on Roosevelt. Documents and letters he had in spades, but the sound, smell and feel of the man . . . that was something else. With the Reagan book, that problem will be solved but at the expense of creating another one. Morris will have the "feel" of the man, but maybe at the cost of perspective. The personality of Reagan, like the height of a Wilt Chamberlain, is an awesome thing. Will even a historian be able to retain historical perspective? We shall see.

Once Morris took me to the Woodrow Wilson Center where he then had a little office. It was there that I discovered that in the age of the word processor, he worked with pen and ink on huge, blank sheets of paper. He wrote and then rewrote and then rewrote some more. The results are evident. Native of Kenya though he may be, his depiction of TR's American West is as evocative of that huge and frightening place as any ever done. The blizzards chill you, the rains soak you, and the vastness diminishes you.

In the White House of today, Ronald Reagan's acolytes suggest one book as required reading: "Lincoln" by Gore Vidal. Its appeal is obvious. Besides being a good book, it depicts Lincoln as Reagan's fans would prefer to see him and, no doubt, as they want history to. He is underrated by his contemporaries, considered a rube from the West and therefore an easy mark for those who naively think they can manipulate the president for their own advantage. But Vidal's Lincoln is shrewd, almost innately so, wise and a remarkable judge of character. He steers his own course, although his compass always remains something of a mystery. What counts is that he gets where he wants to go.

The clich,e holds that time will tell if Reagan is that kind of president, but actually Morris will. As historian-cum- reporter, as both Mr. Inside and Mr. Outside, his Reagan promises to be the definitive one for a long time. The president has chosen well. The secret society of biography buffs offers its bipartisan support.