The Tragic Drama of the Greeks (1896) by the Oxford classicist Arthur Elam Haigh is a comprehensive study of the evolution of the tragic form, covering its origins in the hymns to Dionysus, known as dithyrambs, the activities of the major tragedians of the 5th Century BCE, and later Hellenistic developments at Alexandria and Rome. Although doubtless obsolete as an academic text, Haigh's work has been widely cited over the years, and may still be of interest to the general reader.
Free online texts
Hathi Trust: The Tragic Drama of the Greeks, by A.E. Haigh (1896). PDF format.
Wikisource: The Tragic Drama of the Greeks, by A. E. Haigh (1896). Incomplete, not much more than the contents at the moment.
Wikipedia: Arthur Elam Haigh.
The Great Conversation: Further reading at Tom's Learning Notes