Theodore Roosevelt: A life by Nathan Miller.
The Age of Reform: From Bryan to FDR, by Richard Hofstadter (especially the excellent introduction if the book itself is too much)
A short collection of essays entitled Progressivism by Arthur Link and Richard McCormick
The Era of Theodore Roosevelt by George Mowry.
FDR by Jean Edward Smith but there are a number of well-reviewed biographies that you might prefer.
The chapters on the Roosevelts in Leadership. Lessons from Presidents in Turbulent Times by Doris Kearns Goodwin are definitely worth a read.
The Devil in the White City by Erik Larson
The Jungle, by Upton Sinclair
The novels of John Steinbeck, in particular The Grapes of Wrath
We will also be organizing two cinema evenings – The Age of Innocence, based on the Edith Wharton novel, and Hyde Park on the Hudson
Ken Burns documentary The Roosevelts, An Intimate History, but it does run to approximately 14 hours.