Originally they were silver slippers. That may have been fine for L. Frank Baum's novel, even metaphorical if you believe that "The Wizard of Oz" is a depression-era parable -- and the coveted slippers were the hard currency so needed. But it wouldn't do for showing off MGM's expensive Technicolor. Sometime between the May 9, 1938, script of "The Wizard of Oz" and the May 14, 1938, revision, they became ruby slippers, silk faille pumps, each covered with georgette fabric and 2,300 sequins. The counting of such a thing would be ludicrous -- perhaps you think it still is -- were it not that Dorothy's shoes are an object of obsession. The shoes she got when her house fell on the Wicked Witch of the East -- the ones that the Wicked Witch of the West coveted, the ones that magically got Dorothy back to Kansas when she clicked the heels together three times -- are now considered much more than mere costume. As "The Wizard of Oz" has become an American folk tale, so the ruby slippers have become an icon of 20th-century Americana that auction bidders warred over at Christie's -- and that Rhys Thomas has now written an entire book about. The 32-year-old Thomas, the son of psychologists who teach in California, had been a writer for various short-lived television talk shows. He was searching for a TV story when he began exploring the MGM script library, then being dismantled. The show fell through but he tried to sell a newspaper story about the various script stages of the Oz movie to an editor. When Thomas mentioned in passing the history of the ruby slippers, the editor said, in effect, Forget the scripts, give me the shoes. After a two-part series for the Los Angeles Times, and two years' research, he has now produced "The Ruby Slippers of Oz," one of a rash of Oz-related books that will appear this summer for the 50th anniversary of the movie. (The shoes had already figured in Aljean Harmetz's "The Making of the Wizard of Oz.") "The slippers are really Hollywood's most enduring symbol of belief," Thomas was contending during a recent visit to Washington. Thomas so far has tracked down four pairs of the shoes made for Judy Garland for the film, which took six months to shoot. "Several of the Munchkins I talked to -- who are the only survivors -- said there were six pairs," Thomas says. Various sources have varying figures. "I would say there are definitely four, maybe seven," the author says. He suspects that one pair was destroyed and that at least one more is still out there. But don't even think about it. They're too expensive and too small -- unless you wear a size 5, 5 1/2 or 6 shoe and can afford to match or better the $165,000 price that each of two pairs fetched last summer at auction. "When you start getting into the construction of the shoe you're getting into a very complicated area," Thomas says. It's likely that Hollywood's Western Costume Co. produced the shoes, then sent them over to the MGM wardrobe department. Somewhere along the way, they were embellished with sequins and rhinestones and beaded bows to the specifications of the famous fashion designer Adrian, who was the costume designer on "The Wizard of Oz." The condition and color of the shoes vary. There's no way, Thomas says, to gauge whether Garland wore each pair, and he is unconvinced of a one-time owner's claim that he found scuff marks where Dorothy clicked her heels together. The pair enshrined in the Smithsonian's National Museum of American History is in the worst condition of all, according to Thomas. Three pairs are owned by private collectors, who often show them at galleries, shopping malls and theme parks. Anthony Landini of Lighthouse Point, Fla., who paid $165,000 for his pair at Christie's last June, has them on display at the new Disney-MGM Theme Park in Orlando. Initially, they were not considered valuable. Roberta Jeffries Bauman of Memphis was a high school junior in 1940 when she won a pair (size 6B) in a national "Name the 10 Best Movies of 1939" contest. Thomas speculates that the Bauman pair was worn in Garland's skipping and dancing scenes, since there's orange felt affixed to the sole -- probably so they wouldn't be noisy on the plywood Yellow Brick Road. Bauman's slippers were sold to the Florida buyer. A preliminary ruby slipper -- designed by Adrian and nixed before production -- features dramatic curling toes and heels and jewels all over. The "Arabian test pair," as they came to be known, is apparently owned by Debbie Reynolds, a longtime collector of Hollywood memorabilia. Thomas writes that she never allowed him to see the shoes. It's interesting who doesn't own a pair. None of Garland's children is believed to possess any. Judy Garland didn't either. All the interest in the slippers didn't spare Thomas from some mild ridicule. Reporters who knew what he was working on snickered behind his back. Friends introduced him as "the ruby slipper man." "How can you take anyone seriously who's going to write about ruby slippers?" he acknowledges. "You have to have a self-deprecating sense of humor about this. It's a goofy book and I'm a little goofy for writing it." But in fact his book is not just a history of the slippers. It is also a portrait of the people who came to realize, as the big studios died off, that the costumes from classic movies were pieces of history. "I'm not an Oz fanatic; I'm not a wheeler-dealer of memorabilia, but I fell into this world," says Thomas, a Berkeley graduate in history. He depicts the memorabilia collectors -- not without compassion -- as people who reveled in the movie fantasies brought to life by the costumes they owned and treasured. Their lives were their obsessions -- and some of their homes were garish display galleries. "They at times made me feel creepy," Thomas says. Kent Warner, a costumer whose credits included the movie "Camelot," was well known on the small circuit of collectors. Long before bidders paid thousands of dollars for costumes, Warner hunted through vast studio warehouses and second-hand shops, once finding a dress that Vivien Leigh had worn in "Gone With the Wind" trampled on the floor. Some of Warner's best finds -- a Ginger Rogers fur-lined dress, a Fred Astaire tuxedo -- were salvaged from the rotting RKO wardrobe collections. Thomas writes that many of RKO's costumes were so badly stored they were hung in the studio commissary where patrons would wipe their hands on them. Warner was helping catalogue clothes for the enormous 1970 MGM auction when he found the ruby slippers wrapped in a Turkish towel in a dusty bin on a sound stage. Some of the principals connected to the auction are dead -- Warner died of AIDS in 1984 -- but Thomas's theory is that Warner found several pairs and was told by the man who held the auction to destroy all but one. Thomas also believes that Warner gave a pair to the auctioneers and kept two or three pairs for himself. The best of them he displayed in his living room; another pair he sold to a North Hollywood friend, Michael Shaw, who still owns them. Thomas reports that Shaw was so moved by his acquisition that he cried upon receiving the shoes. Warner put his prized pair up for auction in 1981 and was bitterly disappointed to get only $12,000 from an anonymous California buyer. In his odyssey of tracking down slippers, Thomas ran across a man who claimed he had a pair locked away in a safe deposit box and wouldn't look at them again until he was "worthy." And then there were the Oz obsessives, like a Kansas City newspaper illustrator, Tod Machin. "He's probably the most knowledgeable person in the world about the construction of the shoes," Thomas says. (Machin is the one who counted the sequins on the shoes.) "Tod once said to me, 'Dorothy is a real person and she really grew up in Kansas,' " says Thomas. "I said, 'Tod, please.' " Thomas's chase after shoes crept into his dreams. "I dreamt that I met Marilyn Monroe. Her eyes were blank, she was barefoot and tattered and she told me she had a pair of the shoes." Thomas insists he's doffed the slipper subject for good. "My current obsession is croquet," he says. There's a little grin on his face. However, he is indeed the Beverly Hills Croquet Club champion -- and a rookie on the tournament circuit now. "I will no doubt have other intellectual obsessions. I would say it was an intellectual curiosity that drove me to the point of an obsession. At the point that I realized that this was an unhealthy obsession -- when my friends started asking me for size 10 pairs of ruby slippers -- at that point I said, 'Enough.' " But when he discusses the talk among owners and wannabe owners of the shoes, and when he himself begins to expand a bit dreamily about it, you wonder if he's fully kicked his ruby slipper habit. And since he wrote the book, he's learned that the Smithsonian shoes and Michael Shaw's shoes have mismatched manufacturing numbers that correspond to each other -- meaning the two pairs, of slightly different size, were mixed up 50 years ago. "I just discovered this last week, and it was" -- Thomas searches for the right word -- "remarkable. What it means was Judy Garland was wearing a tighter shoe." He says he's cleared the slipper paraphernalia out of his life. "I own nothing," he says. "In fact, everything I acquired -- all the photos -- I've given away." Thomas says he personally collects old typewriters and first editions of American literature. Thomas owns no copies of the shoes, and he's never even touched a real pair. "At this point, I wouldn't want to." But he still has an eye for ruby slippers. "I see someone wearing red shoes," he says, "and I notice it."