There is a directory of member of the Antiquarian Bookseller's Association, and this directory lists the specialties and interests of its members. Another antiquarian, Bennett Gilbert, works with books which reflect the history of ideas from the renaissance on. If you wander into Heritage Bookshop, a great general antiquarian bookshop, on Melrose Ave, ask to see their personal reference library upstairs. It takes up one entire room. We also here in Los Angeles have world famous research centers like the Getty, the Huntington, UCLA, U.S.C., the Clark Library and others which are staffed by experts who have devoted their lives to the study of the book.
Most libraries have detailed websites that explain their collections.
All are open to the public. Some like the Huntington and the Getty are restricted to advanced scholars, but certainly welcome any visitor who can best be served by using their specific collections. Others like the Clark make their vast resources relating to English culture of the 17th and 18th centuries, Oscar Wilde and the 1890s, and fine printing and the book arts available to anyone. Any reader is accorded the same privileges, apart from the use of our private cubicles, which are reserved for Clark fellows. A reference librarian is usually on call, and the Reading Room supervisor can answer many basic questions.