Read the Kaisetsu (explanations) in Japanese only. Force yourself to understand the grammar explanation in Japanese. This is the unique benefit of this textbook.
Good news: There are legal ways to acquire a digital version. "PDF" does not always mean "illegal." Chuukyuu Kara Manabu Nihongo 3rd Edition Pdf
If you want the efficiency of a PDF without the piracy guilt, follow these steps: Read the Kaisetsu (explanations) in Japanese only
One of the most respected—yet often overlooked—textbooks for this exact stage is (中級から学ぶ日本語), now in its 3rd Edition . now in its 3rd Edition .