It was right after the end of the first Fullmetal Alchemist anime TV series, that I picked-up the manga about six years ago.
The very first chapters went accordingly to what happened in the anime, but once reaching the end of the Fifth Laboratory arc and the Dublith arc the story drastically changed from what I'd watched in the first anime.
I didn't have any idea of who "Father" was in the manga or anime, until Arakawa-sensei introduced the character at the very end of the Dublith arc.
So, here I am folks. My trek around the manga finished yesterday once I read from beginning to end the very last chapter / issue.
What I very much loved about this manga was how Arakawa-sensei kept with the pacing without dragging the arcs or rushing them, and that's same to say about the characters.
She had to wait, until the story came to certain points or situations to properly have the characters start to acting for themselves. I know that she introduced way too much characters and was forced to minimize their performances and apparitions on the panels to allow for more interaction with the protagonists and the main casts, but she never casted away the other characters.
The other thing I liked about this manga was how it kept a balance of strengths. With that I meant with that is that in many typical, battle shounen stories or quests, the hero always can rely upon the friends he or she has met along the journey for help or to get strength from them.
The balance that FMA attained was that the Elric Brothers had to encourage among themselves in the most critical, dire, or grievous circumstances to believe in their own strengths. At times, they were thoughtful about not requiring the help of their buddies, if they realize that their friends would happen to be at the mercy of an inminent danger or jeopardy. However, at times (not all of them) were smart and kind enough to admit at asking for help.
Their burning passion and bravery made their acquaintances to be inspired about them to move on.
If you ask me, from my personal opinion I believe that the story primarily revolved around Hohenheim at finishing what he started. Through Hohenheim the readers were introduced at how all this mess began, ages before the Elric brothers' tragedy.
To be honest, Father made for an interesting and effective villain. It wasn't the "bent on world domination" villain-cliché type. Rather, my theory suggests that Father attempted to become a god itself to escape from whatever laws or rules the universe, the truth, or God imposes to all living and/or non-living organisms.
I believe Father could not bear the thought of being a puppet to a higher intelligence, conscience, or sentience and be manipulated to the whims of that sentience. But at the end, Father reaped what he sowed. Its own conceitedness gave birth to its despair. Father wasn't different from all those humans it crushed, devoured, and swatted like buzzing flies. It used all those souls and life and traded them for energy to build its strength and knowledge, but it never believed in itself at all.