The letters of Charles Lamb were addressed to, among others, William Wordsworth, Samuel Taylor Coleridge, William Godwin, and Thomas Hood, all of whom were close friends. They are valued for the light they throw on the English literary world in the Romantic era and on the evolution of Lamb's essays, and still more for their own "charm, wit and quality".
More than 1,150 of Lamb's letters survive, scattered among institutions and private collections in Britain and the United States. The largest collection, comprising about 200 letters, is in the Huntington Library in San Marino, California. There are very few existing letters addressed to Lamb apart from those sent by his friend Thomas Manning, since Lamb usually destroyed his old correspondence. Lamb wrote his letters in a "bold free hand and a fearless flourish" (his own words), which present no great difficulties to editors, though his spelling and punctuation were sometimes erratic.
Lamb's main correspondents were the poets William Wordsworth, Samuel Taylor Coleridge, Robert Southey, Thomas Hood, Bernard Barton, Mary Matilda Betham and Bryan Procter; the philosopher and novelist William Godwin; the music critic William Ayrton; the publishers Edward Moxon, William Hone, Charles Ollier, Charles Cowden Clarke and J. A. Hessey; the statistician John Rickman; the actress Fanny Kelly; the political agitator Thomas Allsop; the Sinologist Thomas Manning; the lawyer Henry Crabb Robinson; also John Bates Dibdin, member of a theatrical family, and Robert Lloyd from a literary Quaker family. The surviving letters extend over a period of nearly 40 years, beginning in May 1796 and ending only a few days before his death in December 1834. In the first sequence of 30 letters written to Coleridge he minutely criticises his friend's poems, advising him to abandon conventional poetic diction and "cultivate simplicity". The influence he exercised on his friend is seen as crucial in preparing Coleridge for the Romantic revolution that he and Wordsworth launched two years later in their Lyrical Ballads. Almost from the beginning the letters show Lamb's sense of duty to his family and friends, but after a few years, without abandoning his moral convictions, Lamb found a lighter means of expression. In an 1801 letter he wrote, "I have had a time of seriousness, and I have known the importance and reality of a religious belief. Latterly, I acknowledge, much of my seriousness has gone off…but I still retain at bottom a conviction of the truth, and a certainty of the usefulness of religion." In the later letters it is often possible to see Lamb forming and developing the ideas that he later presented in fully matured form in the Essays of Elia and other magazine pieces, and in this way they proved to be essential to his career as a published writer.