The reunification of 10 faculty libraries inside the new Rolex Learning Center at EPFL was a perfect opportunity to rethink which collections should be put forward in an environment that is organized primarly around the working and living space of the users. "Collection development" has shifted from a simple selection of content added to collections to a selection of the best way of access to relevent content. Electronic books allow on-demand access in an even more cost and ressource-efficient way. We discuss how the EPFL Library is implementing its e-books collection to allow for on-demand rental or buying of titles.