The First Amendment of the U.S. Constitution prohibits Congress from passing laws that establish a state religion or restrict the free exercise of religion. It protects freedom of speech, freedom of the press, the right to assemble, and the right to petition the government for redress of grievances. This is a cornerstone of American democratic society and is part of the Bill of Rights added to the Constitution shortly after its adoption in the late 18th century. However, in recent years, there has been a noticeable increase in book challenges in the United States. These challenges involve attempts to remove or restrict access to certain books, often initiated by individuals or groups who object to the content. Most commonly, these challenges aim to remove books from libraries or from educational curricula and materials, thereby limiting access not only for the specific group the book is deemed to "threaten" but also for others who had access to it before. If the attempt goes beyond mere objections and leads to the physical removal of a book, it becomes inaccessible. Fortunately, due to the dedication of librarians, teachers, parents, students, and other informed citizens, most challenged books continue to be available in libraries and educational programs. The American Library Association plays a significant role in promoting freedom of thought and expression, even when those ideas are unpopular in certain communities. Established in 1867, the association has been collecting data on books challenged for various reasons, including "political, religious, racial, sexual, and explicit content," since the 1990s. They rank these challenges by year and reasons for questioning. Their website provides a list of the "Top Ten Most Challenged Books" for each year since 2000. Additionally, they maintain a list of frequently challenged classics and 20th-century authors. They also provide a breakdown of documented book challenges by U.S. states and areas where "banned books" incidents were most prevalent. Troublingly, recent data reveals a rise in book challenges in the United States in 2022, with a 38% increase compared to the previous year. The organization bases its analyses and publications on data sent to them by the American Office for Intellectual Freedom, which operates within the association. Their goal is to inform the public about this pressing issue and to organize various educational initiatives like Banned Books Week. This event brings together numerous librarians, teachers, journalists, writers, publishers, parents, and others with the aim of highlighting which books are being challenged and why. The purpose of this thesis is to provide an overview of challenged books in the United States over the past two decades, analyze the reasons for attempting to remove them from libraries, identify the groups seeking to ban them, spotlight books that have consistently appeared on the "blacklist," and offer insights into potential contentious parts of these books that the author has been able to access. Additionally, it aims to address the clash between American democracy and the growing intolerance of the "other" – those who look, think, read, or speak differently. Are book bans in the 21st century something we should merely accept? Why is this phenomenon so prevalent in a democratic nation like the U.S., and why is it on the rise? Who wants to remove books from libraries, and why? This thesis attempts to answer these questions.