There are only really two modern biographies of Smith: Empire Statesman by Robert A. Slayton (Free Press, 2001) and Alfred E. Smith: The Happy Warrior (Hill and Wang, 2002). The first is generally regarded as a bit better than the second and is written by a history professor.

On my TBR list is the more recent major work involving Smith, The Revolution of '28 by Robert Chiles (Cornell UP, 2018), but my suspicion based on the stated revisionist goals of the author and its reviews is that it's not something that you want to read as an introduction. For the election, you're probably better off looking at some of the Hoover biographies; the Whyte one is very favorable to Hoover but also very detailed.