Why does he want to read these books -- because he wants to read something meaty, something "smart people read" or some "real literature for adults"? Is he trying to get prepared for a college course? Or is something about these particular books really appealing to him? Sometimes a book, even a book apparently "unsuitable", can really speak to someone, so I'm hesitant to say never -- but I'd be pretty dubious about most of the listed books (except Ivanhoe), and I'd also advise against the majority of AP Lit books for a nine-year-old. Too many have themes that at a minimum aren't going to speak to, and may just confuse or upset a nine-year-old, and be discouraging, rather than encouraging a love of reading and development of understanding and reading skills.
I'd prefer to take that ambition and energy and love of reading and direct it towards books that will speak to and promote the kid's understanding. Of course, it depends on your kid. But in my opinion, typical reading lists for adults or later high school students (so AP Lit lists, for instance) are very poorly suited for many super-bright, strong-reader young kids.
I started to make a list of authors or books I or my kids read around age 9 or 10, but my list turns out to overlap so much with the list at that welltrainedmind thread sunnyday already mentioned (see the post by Hive Mind Queen Bee -- list starting with Alice in Wonderland) that I'll instead recommend you look there.
The OP asked for resources to help with screening books: As already mentioned upthread, CommonSenseMedia is quite informative when they happen to have a review of the book you're considering. Study aids such as CliffNotes do tend to be available for a lot of books assigned as high school or college reading, which would be quicker than reading the books. But my advice is even quicker: stay away from AP Lit reading lists or most of what's on intro college course reading lists when you want a good choice for a nine-year-old. The exceptions, when you can find them, are wonderful; but in general, those sorts of late-high-school/early-college reading lists nowadays slant towards the emotionally wrenching: while they have intellectual challenge and literary merit, they're rarely going to pitched right emotionally or thematically for bright but very young readers.
