These are all good resources for learning more about the music from the first half of the twentieth century.  Some are no longer in print, but might be obtained used through the usual online sources.

Short History of Tin Pan Alley Video

Book Title Author Date
A Fine Romance, Jewish Songwriters, American Songs David Lehman 2009
A Pocketfull of Dreams
The Early Years (1903-1940)
Bing Crosby 2001
A Ship Without a Sail (Life of Lorenz Hart)  Gary Marmorstein  2013
A Song For The Season Mary Steyn 2008
America’s Songs (The Stories Behind the Songs of Broadway, Hollywood and Tin Pan Alley Philip Fura/Michael Lasser 2006
American Popular Song, The Great Innovators 1900-1950 Alec Wilder 1972
As Thousands Cheer – The Life of Irving Berlin Laurence Bergreen 1990
Broadway Babies Say Goodnight (Musicals Then and Now) Mark Steyn 1997
Easy to Remember (The Great American Songwriters & Their Songs) William Zinsser 2001
Irving Berlin’s American Musical Theater Jeffrey Magee 2012
Irving Berlin Reader  Benjamin Sears  2012
Irving Berlin And Ragtime America Ian Whitcomb 1987
Jazz, America’s Classical Music Grover Sales 1984
Louis Armstrong, An Extravagant Life Laurence Bergreen 1977
Mark Steyn’s American Songbook Mark Steyn 2008
Musicophilia, Tales of Music and The Brain Oliver Sachs 2007
They’re Playing Our Song (Conversations with America’s Classic Songwriters  Mark Steyn  1973
This is Your Brain on Music – The Science of Human Obsession Daniel J. Levitin 2006
 This Land That I Love  John Shaw  2013