Flying the line Vol 1 and 2.
Having never had a union before, you might find the relationship between whatever company and the union kind of awkward at first. You will figure out rapidly where your bread is buttered as soon as you get on the line and deal with scheduling vs contract admin. It isn't personal, it's just business. The company wants you to make as many widgets as you can and pay you as little as they possibly can; the union wants you to get a market rate for your productivity and value produced work as little as possible at the highest pay rate and stay in the most comfortable hotel imaginable within walking distance of a great bar and several restaurant options, get 6+ weeks vacation ( see above, work as little as possible), full pay disability benefits, zero $$ contribution for health and life insurance and advance their contract as much as they can with each cycle of bargaining.
Flying the Line gives the background on how ALPA came to be and its wins and losses along the way. Even if you don't end up at an ALPA carrier, it's worth it to see what the guys who went ahead of you dealt with to get where the profession is today.