How does a fictional autobiography affect the reader’s understanding of the historical events described in the novel? Does the narrative bring the reader closer to the events described or does the veil of fiction cloud our understanding?

Well, to be fair, it would be extremely difficult to say whether a fictional autobiography would prove to be "more helpful" in regards to its descriptions of historical events than a traditional third person account. There are advantages and disadvantages to each form. However, the autobiography is unique because it brings to the reader's consciousness a deeply personal understanding of history. This is important because every account of history is someone's personal work--even if he or she is trying to be objective as possible.