I have not read his "Intelligent Asset Allocator" yet, and "Four Pillars of Investing" was my first foray into literature of this type. I had been reading this board and the M* Diehards board for a while before I read it so I was already pretty "Bogleized" at that point, I suppose.
I would suggest taking it out of the library first. If you aren't on board with Bernstein when you start, you will be by the time you finish it. There is a lot of historical information in it to support his point of view. He goes on and on (and on and on, and then continues). He makes his case, and then drives it in with a hammer.
Because of that, I feel it is terrifically boring if you are already in agreement with him, but I still recommend it to people. It would be especially good for those who are not completely decided in their investment philosophy.
Already we are boldly launched upon the deep; but soon we shall be lost in its unshored, harbourless immensities. - - H. Melville, 1851.