Despite your political leanings, one can read THE CONNECTION and find that there are a wealth of connections between the international terrorism community. It's very clear that the al Qaeda had a massive network of support -- be it financial, material, or providing training space -- and that the organization was intent upon inflicting harm wherever and whenever it say a truly calculated means. I think that Stephen Hayes has done an exceptional job at gathering together what proven and speculative bits have been exposed, and I think he does an exceptional job at putting it together in a fashion that makes the most sense to the average reader.
While the book tries very hard to show a definitive connection between al Qaeda and Iraq, I'm not completely convinced it hits the nail on the head. Yes, it is very clear that members within the Iraqi intelligence community were aware of al Qaeda, offered them support and training facilites, etc., but what the book falls short of convincing me is whether or not Saddam Hussein was aware and/or endorsed these activities.
More than anything, I think Hayes underscores that, when you're dealing with intelligence, there very rarely is a "smoking gun" ... rather, there's a lot of smoke one has to peer through in order to get to the bottom in order to reach any conclusions.
Kudos to the book for being accessible to the general public: there are an awful lot of difficult names and places (for a non-political thinker and reader like myself). Instead of spending time exploring the background of these folks and places, Hayes concentrates of current events mostly -- 1990s to the present -- in order to make his case.