In his poems, Hillen focuses on the quieter aspects of ordinary human life and natural events, depicting professional images and life plans, gently describing everyday perceptions, life hopes, individual or historical memories, and the sorrow over losses, especially of deceased loved ones. Hillen's imagery, while not excluding surreal moments, primarily draws its materials from a carefully selective naming of actual, not particularly unusual yet always somehow special perceptions. However, in his verses, there often occurs a slight distortion of reality, a minor overlay of factual images and thoughts with a subjectively guided brushstroke. The reader enters a poetic cosmos that he has not encountered elsewhere, where the fine yet crucial difference from the ordinary lies in the special quality of these verses.