Drawing on the fields of organisational theory, information systems and human-computer interaction, this paper proposes a novel perspective for studying information systems usage by individuals in organisations – in this case, in the back office of a major US-based accounting firm. By conceptualising usage as a holistic user experience – a situated and temporally emergent inseparable mesh of behaviour, bodily movements, perception, cognition and affect – the researcher can avoid misleading reductionism and the overly simplistic reasoning of technological or social determinism. To demonstrate empirically the value of this perspective, the paper focuses on the intertwining of two aspects commonly ignored in prior information systems literature – the affective and the material. Building on Pickering’s (1993) “mangle of practice”, and on the literatures on moods (Bless and Fiedler, 2006), identity (Ashforth and Mael, 1989) and sociomateriality (Orlikowski, 2010), the entanglement of human identity, affective states and enterprise systems materiality is examined, based on observational and interview data. The findings suggest that adopting this theoretical perspective facilitates understanding of the complex, situated nature of enterprise systems usage.