Edited to add: Ok, you know what? I'm giving this another star. Because here we are, a month later, and my son is STILL playing "Ark Designer". He's reading books on engineering and robotics and genetics (and lecturing me on same. *sigh*). He's building Arks out of Lego and drawing pictures of them. He even occasionally jokes, "Hello! I'm going to kill you now! Hello!" (that makes sense if you've read the book). 
 C'mon, kid. Admit it already: this book rocked your world and changed your life. 
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 (original review below) 
 Contrary to our usual practice, I rated this book 4 and my son rated it 2. I found it dryly humorous and an interesting exploration of what makes one human. He found it scary. We had several hiatuses because he would get upset and start yelling, which makes it hard to read to him. I tried to discuss that with him, saying, "Surely you felt so strongly about what was happening to Fisher because you cared about him - and isn't that what a good book makes one do? And it did turn out okay, didn't it?" 
 But no, he's having none of it. In fact, I totally cheated by saying he rated this a 2. He told me to give it NEGATIVE SEVEN stars. But that's not really an option, and again, I think his intense fits of passion over this book are an indication that he did get into it, even if he says he didn't. 
 That said: sensitive eight-year-olds may find this book too intense. There are quite a few life-threatening situations, including evil gadgets and an even eviler Intelligence (ye gods, it actually gave him nightmares, The Intelligence). The dry wit eluded him entirely, which surprised me, but he was just too caught up in the peril I guess.