Please feel free to use the PDF files below under the terms specified in the licenses. Everyone is invited to purchase the published versions within his/her budget. I don't earn much by writing books: the point is to help propagate the values of Open Knowledge to the authors and publishers in China, as well as to prove its profitability.
初等代数 (Elementary algebra, in Chinese)
Currently a pipedream. Designed for freshman-level linear algebra in STEM programs. It might incorporate SageMath.
有限 Lie 型群表示理论讲义 (Lectures on the representation theory of finite groups of Lie type, in Chinese)
代数学方法：卷二 (Methods of algebra: Volume 2, in Chinese)
Work in progress.
It will be published by the Higher Education Press (Beijing).
模形式初步 (Introduction to modular forms, in Chinese)
There are some minor differences between the online version and the published one. Please check the PDF above if you spot some typo.