Karrer, Martin. Die Johannesoffenbarung als Brief: Studien zu ihrem literarischen, historischen und theologischen Ort. Forschung zur Religion und Literatur des Alten und Neuen Testaments, 140. Göttingen: Vandenhoeck und Ruprecht, 1986. 354 pp.
Karrer argues that Revelation is a letter. Even from a cursory glance, one notes the letter features of Revelation. Karrer’s work is, in any case, relevant to the study of those elements of Revelation.
Nevertheless, I must admit that I am not fully convinced, despite all Karrer’s arguments.
Many features that are characteristic of a letter are also characteristic of other forms of communication.
An important observation is that Revelation does not open as a letter from the very beginning, and it does not use the first person-second person communication characteristic of letters in the main body (Rev 1:9-22:5). Revelation 2-3 does not employ the letter form, although it is first person-second person communication.
Although Rev 1:4-5a.5b-6 does look like a letter opening, and Rev 22:21 does look an epistolary closing, it does not make Revelation a letter.
Although Pearson and Porter do not refer to Karrer (but to Bauckham, Theology), their evaluation is worth quoting. “This hypothesis is interesting from a generic point of view, and may have some bearing on the generic sub-category (i.e. ‘an apocalypse sent as a letter’), but really does little to affect the overall character of the book. That Revelation would have been produced, according to this view, for specific audiences is in no way different than the supposition concerning other apocalyptic literature.” (Brook W. R. Pearson and Stanley E. Porter, “The Genres of the New Testament,” in: Stanley E. Porter (ed.). Handbook to Exegesis of the New Testament. New Testament tools and studies, 160. Leiden; New York: Brill, 1997.