County or regional trade directories normally list people in charge of different businesses. However, they omit employees, so anyone seeking clerks, labourers and other general workers will be disappointed.
Kelly's 1912 Directory of Derbyshire, Nottingham, Leicestershire and Rutland (S&N £17.95 + £2.50 p&p), is typical in that it contains the usual listings of professionals and tradespeople. As it is later than the last publicly available census, the 1901, it is a useful guide to the location of East Midlanders before the First World War. It is supplemented by three colour maps of the counties.
However, directories for towns and cities are usually much fuller. The London 1880 Post Office Directory (S&N £17.45 + £2.50 p&p), for example, contains the names of the householder of every house in Central London, arranged alphabetically by streets. It does not, of course, include every occupant. There is no index, but the Find facility allows names to be highlighted, thus enabling family historians to locate past relatives.
Londoners were highly mobile and many would have moved house before the 1881 census, so this is a useful tool to point researchers to other sources of information, such as parish and poor law records.