Purpose: The study aims to determine the compatibility of the books with the principles of children's literature by examining the physical, internal structure, and illustration characteristics of the children's poetry books most borrowed from the Nilüfer Municipality Poetry Library and Misi Children's Library. Method: 98 books evaluated within the scope of the research with sampling were borrowed from the Children's Library and Poetry Library. A case study, one of the qualitative research methods, was used in the current work that collects the data through document analysis. Results: According to the findings obtained from the study, 95.9% of the books are medium size, 61.2% are stitched binding, 95.9% are straw paper, and 40.8% have 71 or more pages. When examining the page layout and grammar features, 42.9% of the books were written with single line spacing, 56.1% were written with 12 font size, 91.8% were left-justified, and punctuation marks were used in 55.1%. Regarding the illustrations placed in the books, 88.8% of the cover art is compatible with the content, 73.5% includes emotional expressions in the pictures, 44.9% has colored pictures, 74.5% keeps no pictures on each page, and 60.2%, places pictures and texts on the same page in a way complement each other. Considering the internal structure of the books, 34.7% tackle the theme of 'values' and 64.3% adopt a pastoral style. Conclusion: It has been found that the majority of children's poetry books borrowed from Nilüfer Municipality Poetry Library and Misi Children's Library have author promotion. The most borrowed children's poetry book belongs to Fazıl Hüsnü Dağlarca, and secondly to Mavisel Yener and Aytül Akal. Most of the books have illustrators and Mustafa Delioğlu is the the one who mostly took part in the illustrating process. The publisher that published the most children's poetry books was Yapı Kredi, followed by Can Child. It has been determined that the publication years of children's poetry books are primarily those of 2012 and 2008 and that the majority of the books are first editions. There is no age information in the majority of children's poetry books. Originality: Some studies examine the physical and content elements of children's books. However, studies on poetry books have not been much in the literature. The study is unique in examining the physical and content features of children's poetry books. It is thought that the study will draw attention to children's poetry books and their place in library collections.