Unlike textbooks like Genki or Minna no Nihongo (which teach general conversation), Shin Kanzen Master is laser-focused on test strategy.
While the full retail PDF is copyrighted, you can obtain the content legally for free or very low cost using these methods:
While Shin Kanzen Master is often under copyright, regional library editions (in Canada or Europe) sometimes have digital lending rights.
The N4 level is a bridge. You move from polite forms (Desu/Masu) to complex clauses (Te-form, Tara, Nara, Ba). The Shin Kanzen Master N4 Grammar book deconstructs 50+ key grammar points.
Consider older, public-domain-friendly alternatives like: