Data visualization lies at the intersection of data science and storytelling, enabling us to discern patterns, trends, and outliers that may otherwise remain concealed within spreadsheets and databases. Altair is a Python data visualization library that offers a unique approach to creating visualizations. Its declarative nature allows users to define what they want to see, rather than how to draw it. This simplicity and elegance make Altair an excellent tool for both beginners and experienced data scientists. The objective of the book is not to cover every aspect of the library, but rather to provide a comprehensive guide, with lots of hands-on examples, that will assist you in creating complex multi-view interactive visualizations. By the end of the book, you should be able to create sophisticated applications that can be included in web pages, and transform them, with little effort, in standalone tools.