HBO's True Blood series is based on the popular Southern Vampire Mystery series written by Charlaine Harris. Alan Ball, the executive producer of the onscreen series, has said: "we stuck really, really close to the first book as the basis for the first season. But by episodes 11 or 12 we start to veer into book 2 to just set things up for the next season - if there is one, because it's not official. We're going to stick to the Sookie and Bill story very closely. The other character we're going to experiment with but we'll remain pretty true to Charlaine's story."
They've started "veering" a little early. Episode 3 contains elements from Living Dead in Dallas, the second book in the urban fantasy series. And one of Sookie's sexual dreamscape scenes in the same episode is completely out of character for her. Additionally, some of the more graphic sex scenes (which don't occur in the book) seem out of place.
However that's not surprising when a book is adapted for the small or widescreen. It's almost expected that the director will take creative license and inject his/her own vision into the final product.
Fans of the show can find a few side-by-side comparisons of the True Blood series with the Charlaine Harris books online. Just beware that some sites may contain book spoilers.