The University of Iowa has an extensive digital library in addition to its collection of printed documents and books about the 33rd vice-president:
A major new biography was published in January 2024:
https://www.simonandschuster.com/books/The-World-That-Wasnt/Benn-Steil/9781982127824
This historical study of Truman’s predecessor as VP, Henry Wallace, unveils new evidence from Kremlin archives that became available to Western scholars after the downfall of the Soviet Union. The World That Wasn’t by Ben Steil describes the turmoil in the Democratic Party over Wallace’s Communist associations in America and Russia, which led to his replacement by Truman as the vice presidential nominee in 1944. Truman is highly praised as a much better prepared and qualified VP candidate, who became a better president than Wallace could have been as the Cold War unfolded.
[The abovementioned book had been featured earlier this year in relation to Truman in May.]