Teach Yourself Logic 2017: A Study Guide [pdf]
Just a heads up, this pdf is not a logic tutorial or textbook, but an annotated bibliography.That said, if you got stuck on material implication (practically a topic discussed on the first or second day of logic study), as I did, and eventually were able to understand it, I'd love to know how. (Notice, only if you got stuck first, not if you never had problem understanding it).