Architecting High Usability Applications
Len Bass of SEI and Bonnie John of CMU produced this paper on Usability and Architecture http://www.sei.cmu.edu/pub/documents/01.reports/pdf/01tr005.pdf
It goes beyond assuming that User Experience (UX) is exclusively an issue to be dealt with at the UI layer. In fact, they go to the length of elaborating how end to end Architecture decisions would have impact on overall usability of a system, and taking a holistic approach of looking at trade-off issues between usability and other ‘architecture quality concerns’ such as security, scalability, performance etc.
I personally find it a refreshing read (especially given the abundance of books on ‘designing user interface’ aka ‘eye candy design’), as well as being a good reference catalogue of ‘architectural mechanisms’ that can be used for building ‘high usability’ apps.