Clarissa, or The History of a Young Lady, is a 1748 novel by Samuel Richardson. Composed as a series of letters, it portrays the young heroine's attempt to maintain her virtue and independence in the face of a domineering family, and of the villainous attentions of the libertine Robert Lovelace.
University of Adelaide (Internet Archive): Clarissa Harlowe. EPUB, HTML and MOBI format.
The Guardian: The 100 best novels - No 4 – Clarissa by Samuel Richardson (1748), by Robert McCrum, 14 October 2013.
Librivox: Clarissa Harlowe, or the History of a Young Lady by Samuel Richardson, in 9 Volumes. Public domain audiobook.
The Great Conversation: Further reading at Tom's Learning Notes
Samuel Richardson: Pamela.
Rousseau: Julie, ou la Nouvelle Heloise
Bloom's Western Canon: Clarissa is listed.