Newman is influential and important for many things, including his historical work and his patristic studies (on which see, inter alia, Benjamin King's Newman and the Alexandrian Fathers: Shaping Doctrine in Nineteenth-Century England) which arguably formed an early contribution to the ressourcement movement in the West. Newman is an important figure in helping the West rediscover the Fathers, and thus an early influence on the Orthodox-Catholic move towards unity. He is perhaps best known for his sometimes controverted thesis about the development of doctrine, which some in the East dispute sometimes without having done the work of understanding Newman.
Two or three times this semester I have recommended to students that they must read Newman, and the best place to start is his Apologia Pro Vita Sua, which of course details his conversion to some extent. I have long recommended that book to people whom I know incapable--for many reasons--of following the arguments to their conclusion (i.e., of "going over" to Rome), telling them instead simply to read it for the beauty of the prose, of which Newman was the unrivaled master in 19th-century letters. After reading the Apologia, next read Ian Ker's unparalleled study, John Henry Newman: A Biography.
About this book we are told:
Over the past two centuries, few Christians have been more influential than John Henry Newman. His leadership of the Oxford Movement shaped the worldwide Anglican Communion and many Roman Catholics hold him as the brains behind reforms of the Second Vatican Council. His life-story has been an inspiration for generations and many commemorated him as a saint even before he officially became the Blessed John Henry Newman in 2010. His writings on theology, philosophy, education, and history continue to be essential texts. Nonetheless, such a prominent thinker and powerful personality also had detractors.
In this volume, scholars from across the disciplines of theology, philosophy, education, and history examine the different ways in which Newman has been interpreted. Some of the essays attempt to rescue Newman from his opponents then and now. Others seek to save him from his rescuers, clearing away misinterpretations so that Newman's works may be encountered afresh. The 11 essays in Receptions of Newmans show why Newman's ideas about religion were so important in the past and continue to inform the present.