In general, the Fullmetal Alchemist: Brotherhood series adheres closely to the manga. It doesn't deviate much and presents the plot and characters as they are in the manga. Some minor changes are made for better animation flow, but they don't affect the core of the story.
Fullmetal Alchemist: Brotherhood is known for its close alignment with the manga. It sticks to the original source material, capturing all the important elements. There might be a few tweaks here and there for visual or narrative purposes, but it remains true to the essence of the manga.
The 2009 version of Fullmetal Alchemist follows the manga quite closely. It covers the storylines and character developments from the manga with great accuracy.