The article is a follow-up of the previous publications by Yu. N. Stolyarov “Documentology: The backgrould and development” and “The basic postulates of documentology as the general theory of documents”. The author substantiates the need for developing the library documentology as an individual discipline with its specific subject, specific document definition, and specific content. The subjects of library document studies are the primary and secondary document; technological document; accompanying document; and administrative document (record). The library workflows are based on procedural documents that form the class of administrative documents that ensure the optimal functioning of the library. Administrative documents in the library, as in other legal entities, are grouped into large subclasses: planning, accounting, reporting, personnel, financial documents, etc. Among them, the managerial documents are mostly important as they are to support the entire management process. Beside these subclasses, the accompanying documentation forms the subclass that makes an essential part of the collection, namely technological, and administrative documentation. To separate the fundamental library concepts of the document, the author proposes to adopt a specific definition for each document process. The library collection document is information specific for the library that is fixed or to be fixed. Fixed information refers to the diachronous, discrete documents, information to be fixed (continuously and to be continuously updated) refers to synchronous (existing at the time of retrieval), continuous (having only the beginning) document. The author defines library documentation as the systematized collection of internal documents. The tasks and purpose of these documents are determined by the specific of library technological tasks and functions. The author insists on developing the key provisions and, above all, the terms of library documentology.