The books are ok at best. Most of it doesn't even follow the in-game story.
Also @Guild Mass Effect has 3 books out now...
Which no one has read and which no one actually talks about. Mass Effect weaves its story fine without outside help. If Halo's story is justifiable by "Well there's books for it so it's not shit" then by the Dictators Burn Books property (don't bother Googling it, it's a long story), it's a shit story.