Grammar explained the way it is actually used, not the way it is catalogued. Each page answers one question, shows you the rule working in ordinary sentences, and names the error that sends learners to look it up in the first place.
Every explanation has an exercise attached. Reading a rule and being able to apply it are different skills, and only one of them shows up when you speak.
Which one to use22
A1Beginner
A2Elementary
B1Intermediate
B2Upper intermediate
Reference15
A1Beginner
A2Elementary
B1Intermediate