Fullmetal Alchemist opens with two brothers trying to resurrect their mother, failing catastrophically, and paying for it with a leg, an arm and an entire body. Everything the series does afterwards follows from that one page.
The alchemy system is the most disciplined magic in shonen. Equivalent exchange means nothing is free, which turns every solution into a cost and every shortcut into a moral question. The story is fundamentally an argument about what people are willing to trade.
Hiromu Arakawa's plotting is famously tight - Brotherhood adapts the manga fully and almost nothing in it is wasted. Characters introduced as jokes turn out to matter enormously, and the political backstory pays off in ways set up dozens of episodes earlier.
Alphonse, a soul bound to a suit of armour, is the series' conscience, and the fact that he is the gentler brother despite having lost more is the whole point.
This collection covers Edward, Alphonse and alchemy iconography.