How different is the Vampire Diaries TV Show from the book series?

Now that the second season is over i'm curious to know what every ones opinion is on the books? i have them all and i have mixed feelings from reading them now because I hear that they are completely different. I absolutely love the show i didn't think i would because i'm a big twilight fan and even though VD books came out before i didn't think i would like the show but i do i'm obsessed. Are the books worth reading?