The article considers the topical issues of contemporary literary studies: cycle formation, structural integrity, and performance of various composite forms (cycle, book of poems, collection). The major milestones of cyclization research in the twentieth century are analyzed; the concept of the cycle and related definitions at the present stage is clarified; the correlation of the book and the cycle is determined. The concepts "cycle", "cyclicality", "cyclization" are specified to be formed during the romanticism period but they exist implicitly and are called "a lyrical novel". The logic of the cycle theory development is displayed. At the end of the 19th century a book of poems did not have a clear distinction from a cycle of poems. At the turn of the 20th century a new cyclic formation appeared: a book of poetry as an attempt to simulate the artistic world integrity. Symbolists were the first to point this link of cyclic formations identifying a cycle, an assembly, a book of poetry, collected works. The theoretical and methodological comprehension of the cyclization problem began to form later. In the 1960s the problem of artistic cyclization of lyrics started provoking a new wave of enthusiasm and some research based on the Russian lyrics of the beginning of the 20th century (L.E. Lyapina, V.A. Sapogov). Founding on the poetic texts of collections, theorists determined the transformation degree of cyclic formations comparing to the traditional classical definition of a cycle (for example, by A.S. Pushkin, N.A. Nekrasov, A.A. Fet); they identified complicated cyclic links and features that determine the appearance of this or that genre form. In the 1970s in researchers' works a tradition of cyclization feature identification began to form and lyric cycle definitions were given according to a set of features: the author's set course of composition; independence of works included in a cycle; composition centripetence; the lyrical plot; the lyrical principle of representation. In the 1980s generalization of the collected material and the establishment of the cyclization theory occurred. I.V. Fomenko considered a cycle as a special "genre" formation. The 1990s early 2000s were marked with a high level of research methodology (M.N. Darvin, O.V. Miroshnikova). Cyclic formations were shown from the evolutionary point of view, cycles were differently classified and the first interpretation of terms "cycle" and "lyrical cycle" was invented. The idea of a cycle and cyclic forms became more spread. A cycle was understood not as a genre or a context, but as a "metagenre", possessing different connection degrees. The books of poetry evolution is in motion: from a poem to a cycle, from a cycle to a collection, from a collection to a book and a trilogy. At present, there is no clear distinction of these concepts in research literature because cyclic forms do not have permanent stable features.
