AGAINST THE CURRENT: AS I REMEMBER F. SCOTT FITZGERALD by Frances Kroll Ring (Donald S. Ellis, San Francisco; distributed by Creative Arts Books, Berkeley: $14.95). For the last 20 months of his life, while he lived in a guest cottage on Edward Everett Horton's Encino estate and then in an apartment on Laurel Avenue in Hollywood, F. Scott Fitzgerald hired as his secretary a young woman named Frances Kroll, just out from New York with her family. She sharpened his pencils, made lunch and dental appointments, typed the drafts of the Pat Hobby stories (which kept him afloat financially) and the last, great novel, "The Last Tycoon," he was struggling to finish. Kroll, later as Frances Ring, the longtime editor of Westways magazine, has written an affecting memoir of Fitzgerald when, as Scott Berg says in an introduction to this 155-page volume, he was out of print and at the apogee of his career. He was also, as daughter Scottie Fitzgerald Smith remarks, fighting private demons, "losing the battle--though winning the war." You'd have thought there was little more to be known about Fitzgerald, but the book is like a rediscovered snapshot, bringing a legendary figure into brief, vivid focus, in all his charm, dedication and torment.