If you are using this book to "spishu" (cheat/copy) or just to study better, keep these topics in focus as they are the 6th-grade heavyweights:
The tricky spelling rules that appear in every dictation. 6 klass russkii iazyk buneev spishu
Because it uses a "developmental" teaching style (making you figure out the rule yourself), some students find it confusing and prefer just being told the rule. If you are using this book to "spishu"