N1 grammar is rarely used in daily conversation. If you don't use it, you will lose it. Finding the PDF vs. Physical Copy
While many students search for a "Shin Kanzen Master N1 Grammar PDF" for convenience or quick reference, there are distinct advantages to both formats:
Focus on the "Similar Grammar" boxes. The JLPT loves to test you on two points that mean "because" but have different levels of formality.
Take the example sentences and put them into a flashcard app like Anki.