IF THOMAS JEFFERSON HAD NOT been such a good host, chances are that the President's house now would be in Philadelphia or New York. And we'd all be living in the Port of Georgetown.

In 1790, two questions threatened to dissolve the new Union: the assumption of the pre-Constitution debts of the East (as the northeastern states were called), and the permanent site of the capital, then in New York, but proposed for either Georgetown on the Potomac or Philadephia.

Alexander Hamilton, then Secretary of the Treasury, brought the problem to Jefferson. Jefferson invited the influential politicians to his house, fed them well, perhaps with the ice cream recipe he'd brought from France, and the compromise was made. The Union assumed the debts of the Eastern States. And the capital was located in the South, adjacent to Georgetown, to please the Southern States -- and, incidently, George Washington, a big landowner.

The Jefferson ancedotes is just the first of many great White House stories, told by Ryan and Guinness in this book.

Jefferson and Washington, both much preoccuppied in building their own houses, decided that a competition for the designs of the Capitol and the President's House would produce the greatest buildings. In the United States then, many gentlemen were amateurs of architecture, but few were professionals. Indeed, Jefferson himself, it was discovered many years later, entered the contest anonymously -- and lost. But he was more fortunate than most losers. When he became president, he was able to incorporate many of his own ideas.

Guinness, founder and president of the Irish Georgian Society (and a member of the "Guinness Is Good for You" brewing family) goes into great detail to link the winning design by James Hoban to Hoban's experiences in his native Ireland. Guinness points out the similarities found in the Duke of Leinster's in Dublin, Castletown, just west of Dublin, and several others. Ryan and Guinness, whose earlier book was Irish Houses and Castles, surely are on home ground here, though the comparison does occupy a great many pages.

The first to point out the similarities was Benjamin Henry Latrobe who in 1806 wrote: "George Washington knew how to give liberty to his country but was wholly ignorant of art. It is therefore not to be wondered, that the design of a physician, who was very ignorant of architecture, was adopted for the Capitol and of a carpenter for the President's House. The later is not even original, but a mutilated copy of a badly designed building near Dublin."

The authors go on to tell about the various remodelings of the White House, first after it was burned in the War of 1812, then by succeeding presidents. Some of the more interesting drawings show various schemes put forth by Mrs. Benjamin Harrison to get the president's offices out of the White House, long a goal of President's wives.

The destruction of the original interior, including many strata covered over but preserved, during the Harry Truman rebuilding is described. Today, preservationists shudder to think of the gutting of the original building, with bits and pieces of the old house chopped up and thrown away. Surely the safety of Margaret Truman's piano could not excuse such dismemberment of history.

The book touches on two great White House mysteries: the loss of the great Louis Comfort Tiffany screen from the entrance and the George Washington portrait in the East Room which may or may not be by Gilbert Stuart.

The White House, is no substitute for the excellent White House guides produced by the White House Historical Association (740 Jackson Place, NW). The four books, are cheaper, (for the set: $10 in paperback, $15 cloth) and lavishly illustrated. Though popular rather than scholarly works, they are authoritative. But the new book, though it has little new scholarship, is a handsome hardcover addition to the far too few books about the country's most fascinating home. The bibliography and source list is useful.

Unfortunately, neither of the collaborators seem to be writers, and neither seem to have that great affection and knowledge necessary to light up the subject. A biography of the White House could be one of the great suspense stories of all time -- fire, duels, scandal in high places, ghosts, fraud, women's rights, temperamental artists, devious politicians. Sadly, this book is written neither for the scholar nor the public.