This is a free online resource for learning TLA+. To help both beginners and experienced users, the guide is divided into three parts: The Core: a linear introduction to all of the TLA+ language. It starts with basic operators and gradually progresses all the way to advanced topics. The core is intended to be read linearly: people new to TLA+ should start with the conceptual overview and then work forward from there. People comfortable with TLA+ should skim until they find new material. Topics: “Optional” advanced material. Any individual lesson will be useful to many but not all TLA+ users. Unlike the core, these are designed to be mostly independent of each other. If topics have dependencies on other topics, I will call them out. Examples: Applications of TLA+ to specs, showing both how to write and understand specs.

Source: Learn TLA+ — Learn TLA+