I Am Legend was actually really good. I’ve heard a lot of bad reviews about it, but I don’t think they were all that warrented.
Were there flaws with this film? Of course. Did it stay true to Richard Matheson’s book? Honestly, I don’t know! I’ve been trying to get my hands on the book for TWO YEARS… all the Monroe County Library System seems to have is the graphic novel adaptation. 
Will Smith shines as an actor… and he has to really since for 90% of the film, he’s the only actor (Besides the dog of course).