This study analyzes linguistic adaptation and complexity in terms of congruency and incongruency/grammati­cal metaphor, as defined in Systemic Functional Linguistics, in children’s literature in Swedish for approximately ages one to twelve. Following Hasan (2007), who argues in favor of the relevance of linguistic analyzes of literature, the use of grammatical metaphor is analyzed in relation to literary function and to literary themes of the texts. Furthermore, grammatical metaphor is compared to results from Lundqvist’s (1992) previous study on parts of the data on other measures of linguistic complexity defined as for example aspects of word order and length of words, clause elements, clauses and sentences. The results suggest that congruency is a form of linguistic adaptation in books for young children. However, in line with Nikolajeva’s (2005) critique of the concept of adaptation, the study also shows that the language of children’s literature is not only characterized by simplicity and adaptation to the readers’ young age, but that this kind of literature may display linguistic complexity, in the form of grammatical metaphor, and that other literary aims may override ambitions to use a “plain” language. In some books, the use of grammatical metaphor can be explained in relation to literary themes of the texts, corroborating Hasan’s suggestion of such themes possibly being mirrored in the lexicogrammatical realization of a literary text. The study also shows that grammatical metaphor and the complexity measures used by Lundqvist do not always co-occur in the texts. Differences in nature between the two types of complexity analyzed are demonstrated, displaying how grammatical metaphor is a gradual phenomenon, creating more or less “commonsense” or “uncommonsense” (Halliday & Matthiessen 2014) representations of the world. The results suggest that the lexicogrammatical as well as semantic complexity represented by grammatical metaphor is not only a symptom of complexity in texts but also that grammatical metaphor itself creates complexity. Such uncommonsense representations are suggested to be particularly important in relation to complexity and accessibility of a text.