It is not an addition to Air Law, but covers more specifically ICAO Annexes 6 and 18, in other words more to do with EASA than ICAO.
You may well meet other questions from other subjects - for example, questions that may seem best in POF will be there (as they will in Performance), but with a different purpose - for example, a question might ask why a situation is dangerous rather than what it is.
For fixed wing, it will include Grid Navigation and North Atlantic procedures, so it may be best left until you take Gen Nav, RNAV and Flight Planning to save you learning things out of sequence (depends on your school syllabus).
When you join a company, you will find a lot of the subject matter in your company's operations manual, so don't dismiss it out of hand.