I typically use AR, 100 Book Challenge and Lexile numbers to "rate" books. Unfortunately most of these are better at levelling fiction (your two recent choices aren't showing up anywhere). Has he read a fiction book recently that you found to be a "good fit"? I think the reading level is harder to gauge when most of the self selected reading is non-fiction works, though typically the vocabulary in these is higher.
Magyk is the only fiction he has read and honestly, he read a few chapters before asking me to read it to him because he said he couldn't focus. He was able to tell me where he left off and recite some of what he had read to me to bring me up to speed b"so you can enjoy the story too mom". He really enjoys non-fiction much more and if it is fiction, it tends to be around his grade level. For instance, he will read dinosaur books that are fictional and they would be around his grade level but he prefers non-fiction. He loves to read the news and I had to block news sites that were not geared toward kids (cnn, fox, abc, msn) from his internet browser when he called me to read me an article about capital murder and the death penalty. He has formed an opinion about it (Violence is wrong no matter who is doing it) but I fear the details are too grown up for him.
What concerns me most is that the test (COgat) doesn't seem to be geared for him. You need to be involved in his thought process in order to understand his answers and I don't feel COgat accommodates this. He has a VERY difficult time focusing on things that do not interest him. He is very unorganized and sometimes it seems like he thinks so much and wants so desperately to share his thoughts quickly, that he can jump around discussing 10 different topics, easily, in his mind, associating one with the other. I often times get over-whelmed just trying to figure out what we are talking about or which question i should answer first.
When I first came to this forum a few days ago, I was overwhelmed and frustrated. I believed my son had deeper emotional issues that were causing these problems because I cannot wrap my head around a child who is so smart and yet, so, um, difficult? After reading through many of the posts, my son seems normal....at least relative to the other children spoken of here. I am not the only person who sees this either. BUT, I am the only one living with it and it has become increasingly difficult to do. I'm not concerned that he won't be educated enough, because he obviously does a great job of that and I do everything in my power, and within the scope of my poor wallet to accommodate him. I am concerned that he is socially isolated and FEELS like there is something wrong with him and I am concerned that the school leans toward mediocrity, even when he obviously WANTS to do much more than they will allow him to do. At some point, his education is going to stall out either from lack of interest or just plain resentment and I just want to be ahead of the game. But I DO NOT have the financial resources to pay for special tests and such.
