The book and the TV series clearly differ. 
 1. Hershel is incredibly different. He was much warmer on the show and so getting to know his character here seems more realistic. He's lost so much and he think he's losing his mind. I don't blame him. 
 2. The relationship between Glenn and Maggie happened instantly. On the show it was more gradual, but damn, this one exploded. Don't blame them. Actually the way they're basically like - let's fuck - seems almost normal given their circumstances. 
 3. Carol and Tyreese and Dale and Andrea. So yeah. Not even sure how to describe that. 
 4. Rick and Lori. Lori definitely showed more guilt on the show, appearing to regret what she did ((view spoiler)[Mind you, it was a full affair on the show whereas it's a one night stand here (hide spoiler)]). However, in the book she shows absolutely no guilt. 
 Everything right now is so sad. While I know a lot of what is about to come, it's breaking my heart the more I read it.