This textual material is not a balanced literature

Does the highlighted sentences mean "These art books comprise different types of artworks (war and non-war art) and there is no certain balance between their war and non-war contents so that their non-war contents may be much more than their war contents "?

Context:

Because war art is so vast and still expanding, this book cannot possibly be comprehensive. It does not, for example, provide a complete bibliography on war art, although what it presents is extensive. The three main reasons for this selectivity are relatively simple. First, most writers have examined war art from a generally nationalistic and limiting viewpoint. There are books on British, Canadian, and Australian war art, not to mention South African, German, Japanese, and American. Many of these relate to official or commissioned programmes. In similarly nationalistic veins, the betterknown war artists have had exhibitions at the institutions housing their war pieces, with monographs and catalogues accompanying them. Second, many artists who choose war as a subject also select other topics. In general, their war art is part of a larger body of work and appears in books that cover all their endeavours. This publishing activity comprises a great deal of printed material overall. And this textual material is not a balanced literature. Third, other, less well-known artists choose war as their theme, but their work receives little attention. Virtually invisible to scholars and researchers, their contribution remains in archives.