For more than five years while I was at the White House, it was my privilege to work with Lucky Roosevelt, who was chief of protocol. At least for this Reagan administration social secretary, she prevented protocol errors on more than one occasion.

It was with great surprise and regret, however, that I read Mrs. Roosevelt's book "Keeper of the Gate" and The Post article on the book {"The Perils of Protocol," Style, Sept. 30}. The book was a good read for me, with the exception of one strident chord interjected throughout: criticism of Nancy Reagan. And the number of complimentary comments about the First Lady did not soften the bite.

In one instance, Mrs. Roosevelt is indirectly critical of Mrs. Reagan when she complains about the entertainment for state dinners. "The word was that President Reagan did not like opera or heavy classical music. So our foreign guests were often subjected to has-been popular singers and other marginal performers who were not up to White House standards."

As I was personally involved for 3 1/2 years in the selection process for entertainers, with Mrs. Reagan's final approval, it is hard for me to be objective. But not once was I told to steer clear of classical performers because of the president's tastes. My first priority, set by Mrs. Reagan, was to recommend entertainment that would appeal to each state visitor, and I worked closely with the State Department in determining each visitor's basic likes and dislikes. More generally, I was to work to achieve a good balance of classical and popular entertainment, as Mrs. Reagan felt this mix best represented the great variety of talent making up the artistic fabric of our country.

The high quality of popular artists such as Michael Feinstein, Pete Fountain, Dionne Warwick and Dave Brubeck was our standard fare; and in the classical arena, performing for state dinners were the likes of Itzhak Perlman, Jessye Norman, the Chamber Music Society of Lincoln Center and Leontyne Price.

Another criticism was based on an incorrect assumption. In reference to Donald Regan's writing of Mrs. Reagan's use of an astrologer, Mrs. Roosevelt states that "incidents that once puzzled me fall into place. I was bewildered when dates for state visits had to be confirmed with Mrs. Reagan before they could go forward ... the reasons were always a bit murky."

Mrs. Reagan's involvement in this process was at her own request, and it was simply to ensure that the Usher's Office and White House staff -- the butlers, chefs, florists, etc. -- would not be overlooked because of already scheduled events. I was also involved in this approval process, and as soon as the State Department request for a state dinner date had been approved by the National Security Council and Presidential Scheduling, the request would come to me. I would then send it to the chief usher, who would either approve the date or occasionally say he had a logistical problem with it. After the chief usher had approved the date, I would send it by memo to Mrs. Reagan. The memo would return to me with the date approved invariably for that day or certainly by the next, and I do not recall that she ever rejected a date. Such hold-ups and rejections always took place earlier in the procedure.

It is regrettable that Mrs. Roosevelt, characteristically so exacting in details, would have failed to have checked out this one before printing it, especially as it linked Mrs. Reagan yet again to a controversial issue. In Mrs. Roosevelt's own words of an earlier time, "Fun's fun, but the pummeling of Nancy Reagan has gone on long enough!" LINDA FAULKNER Dallas