Okay kiddo, so a bibliography is a list of books and articles that someone has used as sources for their writing.
Now, the Soviet Union was a big country in Europe and Asia that had a government called communism. After their leader Stalin died, they had a new leader named Khrushchev. During this time, many people wrote books and articles about what was happening in the Soviet Union.
So, a bibliography of the post-Stalinist Soviet Union is a list of all the books and articles that were written about the Soviet Union after Stalin died and Khrushchev became the leader. Basically, it's a list of sources that people can use if they want to learn more about what happened in the Soviet Union during this time.