From the early days of digital textbooks to the rapidly progressing age of Large Language Models, researchers from different areas explored multiple research directors on the crossroads of Textbooks, a traditional learning medium and Artificial Intelligence, a technology that could empower it. These research directions formed a new research area, often referred to as Intelligent Textbooks. The International Workshop on Intelligent Textbooks at AIED 2025, the sixth workshop in the series, aims to bring together researchers working on different aspects of Intelligent Textbooks to exchange complementary insights, review new results, and discuss emerging ideas.