The Complete Comics are a mixed bag. There are some really excellent additions that help flesh out the lore and character stories, and other entries that feel under-developed or pretty much pointless. I could rate the individual comics anywhere from one star to five stars, so it's difficult to rate the omnibus as a whole.
This graphic novel is a fun read if you're a Mass Effect fan, but there's not much here for those who aren't. As I am a fan though, I'm really glad I read through the Complete Comics as it really gave me a deeper appreciation for the characters that I've become so attached to.