The ending
The ending of the novel is the ultimate irony, especially after the revelation of Ursula's purpose, which is to stop the Second World War. She is finally completely aware of her existence in her previous lives, and her purpose is revealed. She makes each perfect step necessary to reach the goal, and, after she does, everything starts all over again with the year 1910, and her birth during a snowstorm. The purpose of the ending is understandable, as it serves to represent the never-ending cycle, the infinity, and the ouroboros. Nevertheless, some might argue in favor of its underwhelming result.
The war
The novel represents the ultimate irony of war. Aside from the obvious futility of it, and there being no winners but only losers on both ends, it serves to show how it all stems from one disturbed mind that exhorts their influence on others, and how it all could be stopped if only one person is taken out of the picture.
