These classics are widely available as free PDF downloads on sites like the Internet Archive and various chess portals:
by Sergey Ivashchenko: A great practical choice for solving puzzles. You can find PDF versions of Chess School 1a which focus on fundamental tactics. kniga kak igrat v shakhmaty skachat
by Ilya Maizelis: A comprehensive manual that starts with the basics and builds toward advanced positional play. It is a staple of traditional training. These classics are widely available as free PDF