Artemis Fowl: Time Paradox

I just finished reading the latest installment of Artemis Fowl. I enjoyed this one and it makes you think about the things you would like to go back and change. But, I'm always in a stupor about some of these time travel things. At least in Back to the Future when he travels back and alters the past his "present" life changed, but why didn't he? In the book Artemis' present life doesn't change like it does in Back to the Future. He just happens to bring back an evil genius pixie with him. So I thought that was wierd.
Artemis's mother has contracted a fairy disease because Artemis used magic on her...or so he thinks. The only cure is brain fluid extracted from an extinct Lemur, which he was responsible for. 8 years prior he kidnapped the last lemur and sold it to the Extinctionists. In order to save his mother he has to go back in time and undo what he has already done and go against himself. Of course, when he comes back he finds out that Opal had taken over his mother's body and had staged the whole thing because she wanted the Lemur's brain fluid so that she could be all powerful and invincible...as all maniacal geniuses want. Artemis discovers that because he went back in time to change all of this he allowed Opal to come to the future and arrange all of this and make it so that Artemis would bring the Lemur to her. He discovers that if he would have left things the way they had happened, things in the present wouldn't have gotten so out of hand. His mother was not in any real danger. I didn't quite understand this whole part...but ok!
The author left it wide open for another book which is great because I really like these books. I wonder what Opal Koboi will do next? What if she releases her present self from confinement? What kind of havoc will this evil pixie wreak on the fairy world? Or the human world for that matter.
Anyway, it was a good book and I thoroughly enjoyed it. I love books that only take me a few days to read instead of a few weeks!