The fourth comic: #776 Persepolis
Sure, this is the second time I read this, but it was worth it. As a biography, the comic takes us through the life of Marjane Satrapi, an Iranian girl and woman growing up in Iran during its revolutions, stuck between a western life she's heard of and experienced and the traditional (conservative) Iranian lifestyles that keeps being enforced more and more strictly.
It's engrossing, not in the least because she isn't ashamed of showing her own flaws. It's entertaining and educational at the same time, wrapping observations in nice vignettes that kept me reading. It feels like an important two volumes to read to understand the situation in Iran at the time, the simple graphics enhancing this even further by keeping everything simple and solemn, as well as evocative.