The following is a short list of books in English that, I believe, represent the best of Brechtian scholarships to date. It's somewhat in the order of scholarly significance I deem recommendable to fellow students who are also in theatre studies and wish to dig a little deeper in this extremely versatile field.

1. Bertolt-Brecht-Archiv. Bestandsverzeichnis des literarischen Nachlaßes. Berlin : Aufbau-Verlag, 1969-1973.

(This is a bibliography of the holdings in the Bertolt Brecht Archive. It provides easy-to-find listings on the sources. It is probably the basis for all serious scholarships since its publication.)
2. Tatlow, Antony. The Mask of Evil: Brecht's Response to the Poetry, Theatre and Thought of China and Japan: a Comparative and Critical Evaluation. Berne: Lang, 1977.

(This is one of the most meticulously researched projects in the field. The title probably appears to be restricted, but in this book Tatlow convincingly shows the importance of the subject to the overall understanding of the Brecht oeuvre.)
3. Völker, Klaus. Brecht, a Biography. Translated by John Nowell. New York: Seabury Press, 1978.

(Völker is from the West, so he is probably free from the hagiographical approaches often seen in similar literatures from the East.)
4. Suvin, Darko. To Brecht and Beyond: Soundings in Modern Dramaturgy. Totowa, N.J.: Barnes and Noble, 1984.
5. Ewen, Frederic. Bertolt Brecht: His Life, His Art and His Times. Reissue ed. New York: Citadel Press, 1992.
6. Willett. The Theatre of Bertolt Brecht: a Study from Eight Aspects. Rev. ed. London: Methuen, 1977.

(Perhaps it needs further updating on the information since it first came out in 1959 (three years after Brecht's death). It focuses on drama and theatre, and provides a lucid enumeration on dramaturgie and literary influence.)
7. Benjamin, Walter. Understanding Brecht. Translated Anna Bostock. London: NLB, 1973.
8. Lyon, James K. Bertolt Brecht in America. Princeton, N.J.: Princeton University Press, 1980. (Very good detective work. The authority on Brecht's literary and political activities in his six-year exile in the States.)
9. Dickson, Keith A. Towards Utopia: a Study of Brecht. Oxford: Clarendon Press, 1978.
10. Milfull, John. From Baal to Keuner: the "Second Optimism" of Bertolt Brecht. Frankfurt a. M.: Lang, 1974.
11. Barthes, Roland. Critical Essays. Translated by Richard Howard. Evanston: Northwestern University Press, 1972.
12. Weber, Betty Nance, and Hubert Heinen.  Bertolt Brecht. Political Theory and Literary Practice. Athens: University of Georgia Press, 1980.
13. Fuegi, John. The Essential Brecht. Los Angeles: Hennessey and Ingalls, 1972.
14. Witt, Hubert. Brecht as They Knew Him. Translated by John Peet. New York: International Publishers, 1974.
15. Berlau, Ruth. Living for Brecht: the Memoirs of Ruth Berlau. Edited by Hans Bunge. Translated by Geoffrey Skelton. New York: Fromm International, 1987.
16. Willett, John. Brecht in Context: Comparative Approaches. London: Methuen, 1984.
17. Parmalee, Patty Lee. Brecht's America. Columbus: Ohio State University Press, 1981.
18. Adorno, Theodor and Hanns Eisler. Composing for the Films. Oxford: Oxford University Press, 1947. Reprint. Atlantic Highlands, NJ : Athlone Press, 1994.
19. Brooker, Peter. Bertolt Brecht: Dialectics, Poetry, Politics. New York: Croom Helm, 1988.
20. Subiotto, Arrigo. V. Bertolt Brecht's Adaptations for the Berliner Ensemble. London: Modern Humanities Research Association, 1975.
21. Betz, Albrecht. Hanns Eisler Political Musician. Translated by Bill Hopkins. Cambridge: Cambridge University Press, 1982.
22. Ley, Ralph. Brecht as Thinker: Studies in Literary Marxism and Existentialism. Normal, Illinois : Applied Literature Press, 1979.
23. Münsterer, Hans Otto. The Young Brecht. Translated by Tom Kuhn and Karen J. Leeder. London: Libris, 1992.
24. White, Alfred D. Bertolt Brecht's Great Plays. London : Macmillan, 1978.
25. Hill, Claude. Bertolt Brecht. Boston: Twayne, 1975.

The following is a list of books in German which, even though with minimum knowledge of the language, all potential students need to become familiar with. Some of them have numerous illustrations or pictures that might prove useful in research. No particular order.

Berlau, Ruth, et al, ed. Theaterarbeit. 6 Aufführungen des Berliner Ensembles. Dresden: VVV Dresdner Verlag, 1952. 3rd ed. Berlin: Henschel, 1967. Eisler, Hanns. Gespräche mit Hans Bunge: Fragen Sie mehr über Brecht. Ed. by Hans Bunge. Leipzig: VEB Deutscher Verlag, 1975. Gersch, Wolfgang. Film bei Brecht: Bertolt Brechts praktische und theoretische Auseinandersetzung mit dem Film. Munich: Hanser, 1975. Hecht, Werner. Brecht Chronik: 1898-1956. Frankfurt a. M.: Suhrkamp, 1997. Hennenberg, Fritz. Dessau-Brecht musikalische Arbeiten. Berlin: Henschelverlag, 1963. Hurwicz, Angelika. Brecht inszeniert: Der kaukasische Kreidekreis. Velber bei Hannover: Friedrich Verlag, 1964. Kaufmann, Hans. Bertolt Brecht: Geschichtsdrama und Parabelstück. Berlin: Rütten and  Loening, 1962. Knopf, Jan. Brecht-Handbuch: eine Asthetik der Widerspruche. Stuttgart: Metzler, 1980-1984. (The standard reference book in the field. It provides detailed synopsis and analysis on major Brecht writings. Another project is currently under way to replace this Handbook. But until then...) Mayer, Hans.  Brecht. Frankfurt a. M.: Suhrkamp, 1996. ("Brecht und die Tradition." Translated by Jack D. Zipes in Steppenwolf and Everyman. New York: Crowell, 1971.) Niessen, Carl, ed. Brecht auf der Bühne. Cologne: Institut für Theaterwissenschaft der Universität Köln, 1959. Rülicke-Weiler, Käthe.Die Dramaturgie Brechts: Theater als Mittel der Veränderung. Berlin, Henschel, 1966. Schumacher. Die dramatischen Versuche Bertolt Brechts, 1918-1933. Reprint. Berlin: Das  europaische Buch,1977. Steinweg, Reiner. Das Lehrstück: Brechts Theorie einer politisch-asthetischen Erziehung. Stuttgart: Metzler, 1972. (The standard book on this particular genre. Recently the views have been challenged by another book: Krabiel, Klaus-Dieter. Brechts Lehrstücke: Entstehung und Entwicklung eines Spieltyps. Stuttgart: J.B. Metzler, 1993., but the documents collected are still useful.) Wyss, Monika. Brecht in der Kritik: Rezensionen aller Brecht-Uraufführungen, sowie ausgewählter deutsch- und fremdspracher Premieren. Munich: Kindler, 1977.

happy end: 11.08.1999.