This is a pretty good read. Like someone else mentioned in a review, you don't need any prior knowledge of the anime to read this. (I actually got about 4 volumes in before I saw the anime)
Now, the introduction of the characters, the extra view into each person's thoughts (Shinji: ''third child? What's she talking about'')Are pretty cool, but ultimately, where I feel that the book suffers is in the ability to convey the action scenes, which obviously can't come close to the way they are done in the anime.
However, aside from this, it's a REALLY good read, and it's becoming increasingly obvious as I get further in that the story is definitely different to the anime, and may even end differently.
There are lots of extras from the western translators to make up for the wait for it to come out, and they are pretty good too, such as, in volume 9, a reference to a mark twain story, and analysing how it may have influenced the creation of Kaworu Nagisa, as well as a mythology segment in one of the current mid point volumes that examines the references to religion covered by eva.
Overall, it's a must read for fans, and I must say, don't worry if anyone more experienced in these worlds tell any newcomers to wait before getting into eva, it was one of my first series, and remains my favourite to date. Enjoy! ^_^