I’m thrilled to announce that our book with ChengXiang Zhai “User Simulation for Evaluating Information Access Systems” has been published (a preprint is available on arXiv). This comprehensive monograph delves into the pivotal role of user simulation in assessing the effectiveness of information access systems, such as search engines, recommender systems, and conversational assistants. Addressing the intricate challenges of evaluating these systems, our book explores user simulation techniques that account for the diverse behaviours and preferences of users. It offers a detailed examination of general frameworks, models, and algorithms designed to simulate user interactions, and establishes connections with related fields, including machine learning, dialogue systems, user modeling, and economics. We also discuss future research directions that extend beyond the evaluation of information access systems and are expected to have broader impact on how to evaluate interactive intelligent systems in general.