"Ultimatum" is a science fiction novel written by Ukrainian writer Oleksandr Zorin. This book tells about the near future, where humanity faces a threat from alien civilizations. The main character, theoretical physicist Maxim, accidentally discovers a secret government project aimed at developing weapons against aliens. After that, a mad race for technology and power begins between countries that want to take advantage of the new find. In this book, the author not only reveals an exciting plot, but also asks the reader important questions about the future of humanity, its moral principles and responsibility for one's own actions. "Ultimatum" is an exciting adventure that will leave you thinking long after the last page.