Flightless bird. Download AC64-7, and print off the exam syllabus for ATPL Law. It lists all examinable material. Go through this list, and beside each subject make a brief note of the required knowledge. It's mainly questions from CAR 91, 125, 121, and AIP ENR, all of which is availiable for free online. Nothing at all difficult. I scored a good pass this way, with not an unreasonable amount of effort. (Few days). This way you can be confident you've covered all possible material, most of which is basic commercial law.
And you don't need hard copies of Vol 2 and 3.
Good luck.