yes, it is. To sum it up, the original was at about 50-60% true to the manga half way through, then went 100% away from it, changing how homonculus was made and even changing the homonculus themselves. In brotherhood, it is 99% accurate to the Manga. maybe even 100%.
give it a try, you'll see similarity's in the first 5-10 episodes, and a few after that, but then it starts getting into the real story of FMA