(I'm cramming three volumes of Fullmetal Alchemist for my book club this afternoon! I'm reading the omnibus but I'm going to log each volume as a separate entry to contribute to my reading goal.)
Ugh. This volume. It contains the introduction of Scar, the scenes with Dr. Marcoh and his village and, of course, the infamous Nina Tucker chapter . (Not in that order.) Despite the emotional weight of these plot points, the story still manages not to get too oppressively heavy. (Though, I did tear up a little bit in the office.) It's easy to chalk up the smooth tone to the relationship between Ed or Al or even the comedic value of Ed's rivalry with Roy Mustang, but I think FMA is just well-crafted enough not to be overpowering.
I love how complex this story is, just in general. You've got at least half a dozen themes going on here-- the consequences of war, the militarization of science, what it means to be a human, the danger in religion controlling a state, etc. -- but they all meld well and manage to be a pleasant reread. As I recall, the next volume has some lighter moments so I look forward to those!