Toscanini, (1978) Harvey Sachs, Philadelphia: J. B. Lippincott Company.
The definitive biography.

Reflections on Toscanini, (1991) Harvey Sachs, New York: Grove Weidenfeld.
Additional material to complement the original biography.

The Letters of Arturo Toscanini, (2002) Harvey Sachs, New York: Alfred A. Knopf.
Correspondence with his wife, children, colleagues, friends, and lovers.

Arturo Toscanini: The NBC Years, (2002) Mortimer H. Frank, Portland Oregon: Amadeus Press.
A complete description of all the NBC broadcasts. There are quite a few errors that I have noted here.

This Was Toscanini, (1963) Samuel Antek, New York: The Vanguard Press.
Indispensable, the source of all of the great Hupka photographs.

The NBC Symphony Orchestra, (1938) Introduction by Hendrik Willem van Loon, New York: National Broadcasting Company.
History of the orchestra and biographies of personnel. Contains charcoal portraits by Bettina Steinke.

Conversations with Toscanini, (1959) B. H. Haggin, New York: Doubleday & Company, Inc.
Fascinating insight from an excellent music essayist.

The Toscanini Musicians Knew, (1980) B. H. Haggin, New York: Horizon Press.
What some of his colleagues thought.

Portraits of Greatness - Toscanini, (1987) John W. Freeman and Walfredo Toscanini, New York: Treves Publishing Company.
An excellent brief softcover bio with lots of photographs.

Toscanini and the Art of Orchestral Performance, (1956) Robert Charles March, Philadelphia: J.B. Lippincott Co.
A brief bio, performance analysis and a US repertoire list for the years 1925 to 1954.

Arturo Toscanini, (1982) Denis Matthews (with selected discography by Ray Burford), New York: Hippocrene Books.
Another short bio, this time with a discography with comments.

Toscanini, (1975) George R. Marek, New York: Atheneum.

Toscanini, (1936) Paul Stefan (Translated from the Austrian by Eden and Cedar Paul), New York: The Viking Press.
A short book with some good insights written before Toscanini conducted the NBC Symphony.

Toscanini and Great Music, (1938) Lawrence Gilman, New York: Farrar & Rinehart.

The Magic Baton, (1957) Filippo Sacchi (First Published in Italian), New York: G.P. Putnam's Sons.

The Story of Arturo Toscanini, (1960) David Ewen, New York: Holt, Rinehart and Winston.

The Maestro, (1951) Howard Taubman, New York: Simon and Schuster.

The Toscanini Legacy, (1969) Spike Hughes, New York: Dover Publications, Inc.
Performance analysis of a number of works.

Toscanini: An Intimate Portrait, (1956) Samuel Chotzinoff, New York: Alfred A. Knopf.
There are a million copies of this, but don't bother.

Arturo Toscanini, (1929) Tobia Nicotra (Translated from the Italian by Irma Brandeis and H.D. Kahn), New York: The Sun Dial Press, Inc.
Another early biography.