This is a bundle of three classic commentaries on Revelation, each the product of a series of Lectures on the book, combined to make a continuous Commentary. Each is the work of a distinguished scholar and minister, offering considerable insight and learning, despite following different approaches of interpreting the book.
The work by John Cumming (1807-1881), published in 1854-5 under the heading Apocalyptic Sketches, is an extensive 2-volume combination of lectures (covering more than a thousand pages in print). Largely influenced by E. B. Elliot's massive 4-volume Horae Apocalypticae, Cumming adopts a similar church-historical approach to Revelation, generally interpreting the various visions as predicting different periods of Church History, from the time of the original writing to the mid-19th century, with special emphasis given to the Protestant Reformation and its aftermath.
The lectures by William Kelly (1821-1906), published in 1903, adopt a more standard futurist approach to the book—indeed, Kelly writes specifically against the church-historical mode of interpretation (of Elliot, etc). As such, modern-day readers and students are likely to find his analysis and exposition more familiar. It contains much detailed exegesis, though for the most part the Greek text is dealt with only in the footnotes.
The lectures by William Milligan (1821-1893), published in 1892 (from his Baird Lecture of 1885), take a more critical approach to the text of Revelation, though most of the lectures deal with the book as a whole, rather than on exegesis of individual passages. It thus serves readers more properly as a thorough, criticial Introduction to Revelation; however, chapters 19:11-22:5 are examined in more detail in the final lecture.