Stop One: Alter Ego
Go to the source. See the TwoMorrows Bibliography, which lists the relevant issues of Alter Ego that feature Jim Amash's original interviews and other Quality-related articles. Most of those issues are available for digital download.
And it couldn't be easier for you to start clicking on the Online Resources.
Stop Two: Defintive Works
Park yer carcass for a weekend with these books in your hands. The following publications are definitive and recommended works.
Black, Bill, ed. Golden Age Greats Spotlight, vol. 2. AC Comics, 2007. Reprints loads of complete Quality Comics stories.
Chabon, Michael. The Amazing Adventures of Kavalier & Clay: A Novel. New York: Random House, 2000. Though it is fictional, Chabon's own Golden Age research shines through in this Pulitzer Prize winning novel.
Eisner, Will. The Dreamer: A Story from the Birth of Comic Books. Princteton, Wis.: Kitchen Sink Press, 1986. This story was written as an allegory to Eisner's early days with Iger and Quality.
Jones, Gerard. Men of Tomorrow: Geeks, Gangsters, and the Birth of the Comic Book. New York: Basic Books, 2004. An exceptionally well-researched account of comics' (especially DC's) early days.
Spiegelman, Art and Chip Kidd. Jack Cole and Plastic Man: Forms Stretched to Their Limits. New York: DC Comics, 2001. This book covers pretty much everything you'd want to know about its subjects... a definitive work.
Steranko, James. The Steranko History of Comics vol. 1. Reading, PA: Supergraphics, 1970. This volume largely covers the big players, DC and Marvel.
Steranko, James. The Steranko History of Comics vol. 2. Reading, PA: Supergraphics, 1972. This volume contains one of only two known conversations with Quality publisher Busy Arnold, and probably the only published interviews ever conducted and superstar artists Reed Crandall and Lou Fine. Topics: the Marvel Family, Fawcett heroes, Blackhawk, "Flying Heroes," Plastic Man, Quality heroes, and the Spirit.
Stop Three: Deeper CutsThese items might be more reference type materials, things that have minor but significant Quality-related tidbits, or deal more generally with the Golden Age.
The Who's Who of American Comic Books vols. 1-4. Detroit, Mich.: 1973–1976. These four self-published volumes laid the groundwork for all current comics indexing. They have been digitized and updated online.
Brennan, T. Casey. "The Untold History of I.W. Comics." The Comics Journal 57. Summer 1980: 118-119.
Disbrow, Jay. The Iger Comics Kingdom, Blackthorne Publishing, Inc. 1985. Also read this in Alter Ego #21!
Feiffer, Jules. The Great Comic Book Heroes. The Dial Press, Inc., 1965. A comprehensive look at the Golden Age.
Golden Age Men of Mystery #12. AC Comics. 1999. Contains: "I Wouldn't Change a Thing!" An interview with Chuck Cuidera. Reprint of a 1977 redrawing of Paul Gustavson's Human Bomb origin story (Police #1) by C. C. Beck., done in honor of Gustavson's death. Reprints from Quality.
Goulart, Ron. Comic Book Culture: An Illustrated History. Collectors Press, 2000.
Goulart, Ron. "Looking Back on the Golden Age: The Quality Gang: Part 1." Comics Feature 27. Jan.-Feb. 1984: 44-49.
Goulart, Ron. Ron Goulart's Great History of Comic Books. McGraw-Hill/Contemporary, 1986.
Jerry Iger's Golden Features #1-6. Blackthorne Publishing, Inc. 1986-Jan. 1987. Exclusive reprints and unpublished material from Jerry Iger. Issue #2 features Wonder Boy.
Keltner, Howard. Golden Age Comic Books Index: 1935-1955. Gainesville, TX: Howard Keltner, 1998. A staggering self-published tome that indexes almost every Golden Age comic book, including feature titles and page counts.
Rhoades, Shirrel. A Complete History of American Comic Books. Peter Lang Publishing, 2007.
Robbins, Trina. The Great Women Super Heroes. Kitchen Sink Press, Northampton, Mass., 1996. This work touches on USA, Doll Girl, Wildfire, and Phantom Lady.
Sadowski, Greg. Supermen!: The First Wave of Comic Book Heroes 1936-1941. Fantagraphics Books, 2009. Touches on some Quality creators, among others.