Social robots are becoming increasingly integrated into public spaces such as libraries, offering opportunities to enhance services and foster meaningful interactions. Designing a positive user experience (UX) that addresses factors like well-being, comfort, and perceived control is critical to their acceptance. This study presents a Wizard-of-Oz (WoZ) field experiment (N = 64) conducted in two public libraries, exploring key UX dimensions, including pragmatic and hedonic qualities, attractiveness, perceived control and privacy concerns. Findings indicate that pragmatic and hedonic qualities significantly influence the intention to use social robots in libraries, while perceived attractiveness plays a minor role. Moreover, high perceived control positively correlates with a favorable UX, even when privacy concerns are present. These insights inform specific design implications to improve the usability and application of social robots in public spaces. By addressing user needs and fostering trust, this research contributes to the successful integration of social robots into everyday environments, supporting their role in creating more engaging public spaces.