A. Gladkij‘s “Introduction to Contemporary Logic” was printed by a very academic publishing house, but the paradox is that it is probably the most comprehensive textbook on logic of all I ever taught by.
And I would definitely recommend it as a self-study source to anyone trying to understand this seemingly impenetrable science.
You just start reading, and little by little you plunge deeper and deeper: all the terms are explained duely, there is none of that usual touch like “If the author wants me to know it all already, what for would I start reading it then?”
English title: A. V. Gladkij “Introduction to Contemporary Logic”
Original title (Russian): А.В. Гладкий “Введение в современную логику”
First published in the Levinarium Telegram Channel (now closed and deleted)