The dictionary responded to a large extent to a widely felt need for stability in the language. Work on the dictionary lasted for about eight or nine years. An important innovation was to illustrate the meaningss by literary quotation. Most frequently, Johnson quoted Shakespeare, Milton and Dryden.
Unlike most modern lexicographers, Johnson sometimes introduced humour or prejudice into his definitions. Among the best known are "excise: a hateful tax levied upon commodities...", "lexicographer: a writer of dictionaries, a harmless drudge...", and "oats: a grain which in England is generally given to horses, but in Scotland supports the people".
Johnson's etymologies were usually poor by modern standards, and he gave no guide to pronunciation. His dictionary was unashamedly prescriptivist and linguistically conservative, advocating traditional spellings rather than the simplifications favoured by Noah Webster a century later.
In spite of whatever shortcomings it might have, however, the dictionary was far and away the best of its day, a milestone in English-language lexicography to which all modern dictionaries owe some gratitude. Editions of it were widely used well into the nineteenth century.
Contemporary selections from Johnson's Dictionary are available in Samuel Johnson's Dictionary, ISBN 0802714218.