A Warning is a book written by an anonymous author. The author is a senior official in Donald Trump’s presidential administration. In the book, the author provides a comprehensive portrait of Donald Trump’s unfitness to be President of the United States. The author cites Trump’s profound character flaws and the many destructive actions that Trump has taken as the president. The author provides many substantiating details, including both public information and observations from within Trump’s administration. The author hopes that the book will dissuade people from reelecting Trump in 2020. The book explores themes of politics, morality, democracy, and authoritarianism.