forallx: the Mississippi State edition is an open source logic textbook. It covers propositional logic and introduces (although does not cover in as much depth) first-order logic. The textbook is avaialbe as a PDF. Or a paperback copy can be purchased here. The source files, which can be downloaded and modified, are available in this GitHub repository.

Further explanation of this textbook is here. A description of the logic system for this textbook that can be used in Carnap is here.

Here is a syllabus, and here is a more detailed calendar.