Vol. 1 of this commentary features a more than 200 pages introduction covering everything from textual criticism to the langugage of Revelation in more detail than any other newer commentary to Revelation and more than 350 pages of commentary covering Rev 1-5.
Vol 2. is of approximately the same size. A number of excursuses deals with major subjects e.g. the Nicolaitans. The wealth of material, bibliographies, research summaries, as well as Aune’s deep knowledge of ancient literature makes this commentary a must for all serious Revelation students and researchers while it is, in my opinion, of more limited value for homiletic and biblical-theological purposes. It is probably one of the most important commentaries since the commentaries by Bousset, Swete, Beckwith, and Charles, rivalled perhaps only by the commentary by Gregory Beale.
For all its worth, however, some deficiencies may be noticed as well. First and foremost, too often the commentary lacks comments on the text itself and its meaning within Revelation, i.e. the synchronic dimension. The diachronic problems play an immense role, and Professor Aune argues a two-stage composition of Revelation. On a greater diachronic scale, John’s use of the Old Testament is poorly treated in spite of the extensive research (cf. Review of Biblical Literature (2000) (direct link here)