Diary of historian S.A. Piontkovsky is a unique historical source. These are the records of an eyewitness and participant in the creation of Soviet historical science in the 1920s - early 1930s. Undoubtedly, the book will attract the attention of not only professional historians, but also a wide readership interested in studying the understanding of the events of those years, the relationships of colleagues who created the first Soviet textbooks and works on history of Soviet society. Piontkovsky rarely wrote in his diary, so he tried to reflect the most important events and processes in his opinion that he experienced and observed in the past weeks and months. Thanks to this, the records do not contain fragmentary everyday information, but a more holistic picture.