Determined to make her novels as accurate as possible, Heyer collected reference works and research materials to use while writing. At the time of her death she owned over 1,000 historical reference books, including "Debrett's" and an 1808 dictionary of the House of Lords. In addition to the standard historical works about the medieval and eighteenth-century periods, her library included histories of snuff boxes, sign posts, and costumes. She often clipped illustrations from magazine articles and jotted down interesting vocabulary or facts onto note cards, but rarely recorded where she found the information. Her notes were sorted into categories, such as Beauty, Colours, Dress, Hats, Household, Prices, and Shops; and even included details such as the cost of candles in a particular year. Other notebooks contained lists of phrases, covering such topics as "Food and Crockery", "Endearments", and "Forms of Address." One of her publishers, Max Reinhardt, once attempted to offer editorial suggestions about the language in one of her books but was promptly informed by a member of his staff that no one in England knew more about Regency language than Heyer.