[Reposted] The first edition of An Introduction to Formal Logic did logic by trees. The main text of the second edition will do natural deduction, Fitch-style. But chapters on truth trees will still be available, as two online appendices. And these appendices will, indeed, together make a brisk stand-alone introduction to logic by trees for a reader who knows the basics about the languages of propositional and predicate logic.
Here, then, is the first appendix, on propositional truth trees (pp. 27). This is a slightly revised version from the one posted a few days ago. It is free to use and distribute. And the plan is for it to remain freely available, through the IFL2 page. Needless to say, all further comments/corrections gratefully received.