Since the exact 2nd part is not officially titled the same for all editions (often the 2nd part focuses on in C), this content reflects the logical progression after his first book (which covers basic C, loops, arrays, functions, strings, and basic file I/O).
This is a critical point of ethics. Tamim Shahriar Subeen has officially released free PDF versions of his books for personal use during specific events (like national programming camps) and pandemic relief. However, (subeen.com) or his blog first.