The list below contains the most influential books I have read during my professional carrer. It is a mix between books on methodolgy and on user interface development which pretty much summarize what I do:
Agile Software Development: The Cooperative Game by Allistar Cockburn
Implementing Lean Software Development: From Concept To Cash by the Popendieck’s
Laws of Simplicity by John Maeda
Psychology of everyday things and Emotional Design by Donald A. Norman