Ah, the book people love to hate.
Personally, I had no problem with it, thought it was a fun read, although I liked Angels and Demons much better.
Concerning the first paragraph, I think it needs to be read more carefully. It states that there was a real priory of Scion, which Flippy's link also says. It then goes on to say that a document was later found that linked a bunch of famous names to the Priory. This is also true. It conveniently leaves out the fact that that this document was found to be a hoax, but then again, it never states that the document that was found was legit, only that it was discovered.
In other words, the two sentences in the first paragraph are technically true but when they are put together, they don't say what they are appearing to say, if that makes sense. At least that's my take on it.