I picked up the first three books of this graphic novel series because I enjoyed the television show so much. I knew the show deviated from the books because the writers and creators wanted to offer something new - other possibilities.
The start of this book was quite similar - Rick wakes in the hospital to find that everything and everyone he knew had changed. The area was over run by zombies and his family was gone. He goes to Atlanta to find the city is a waste land. He is saved by a young man, Glenn, who takes him back to a camp where Rick's family happens to be with Rick's best friend Shane.
The graphic novel moved much faster and had far fewer plot details than the series. Most of the series is book 1 which is not that big of a book. There were some differences - there's no plot about the brothers (one of them is left handcuffed to a pipe in the city in the show) and at the end of book 1 Shane is killed. That shocked me the most (and sorry for the spoiler but what's more interesting is who kills him).
Other than those two the book and the show are neck and neck.
I enjoyed this book and have already started book 2. My only complaint would be that the book is drawn in black and white which makes details a little difficult sometimes. It's not as distracting to have it in black and white but I think I would have liked some color - some dramatic art to go with the plot (but then maybe that's why we have the tv show).