This article investigates the decision process used by university presses when selecting or deselecting e‐book vendors for academic libraries. It focuses on three research questions: (1) which vendors' university presses worked with; (2) how university presses used different vendors; and (3) why university presses worked or did not work with certain vendors. A series of one‐on‐one interviews were conducted with 19 participants from 18 different university presses in the US. Findings show participants use a core of vendors identified as the ‘Big Four’ plus several other ‘optional’ vendors. The reasons that encourage and discourage presses to work with certain vendors are investigated and reveal a mutual reinforcement cycle that explains the process by which the Big Four vendors became both the main distribution vendors for university presses and the main providers for academic libraries for e‐books in humanities and social science. The research also discusses efforts made by several university presses and other vendors to challenge the dominance of the Big Four.