International audience This paper focuses on novels addressed to that category of older teenagers called "young adults", a particularly successful category that is traditionally regarded as a subpart of children's literature and yet terminologically insists on overriding the adult/child divide by blurring the frontier between adulthood and childhood and focusing on the transition from one state to the other. In Britain, YA fiction has developed extensively in the last four decades and I wish to concentrate on what this literary emergence and evolution has entailed since the beginning of the 21 st century, especially from the point of view of genre and narrative mode. I will examine the cases of recognized-although sometimes controversial-authors, arguing that although British YA fiction is deeply indebted to and anchored in the pioneering American tradition, which proclaimed the end of the Romantic child as well as that of the compulsory happy ending of the children's book, there seems to be a recent trend which consists in alleviating the roughness, the straightforwardness of realism thanks to elements or touches of fantasy. We will explore the way the two narrative modes of realism and fantasy often merge in British YA fiction, coming close to what could sometimes be called "magic realism" or mingling subgenres to produce experiments in form that suggest the particular state of young adulthood. By creating textual hybridity, these generically ambiguous novels mirror the in-betweenness of their intended audience.