I, Sniper's a fine one to get re-introduced to the character. Hunter's at the top of his form, much better than I remembered. Plenty of nuts and bolts about sniper guns and the manly art of sniping as well as a highly effective scene of waterboarding that reaches the height of art. And I'm not kidding. The Wikipedia article I linked to describes his prose as almost lyrical and though that might be strange for the thriller genre, I think it's spot on. Overblown in parts, sure, but you can tell Hunter is passionate about his subject and I like passion. He takes a few sly potshots at the media and liberals, too, so that's an extra bonus if you're looking for that sort of thing.
Of course, the problem with entering a series in the latest installment is that the author has to bring new audience members like me up to speed with his character and, having done so, there's little reason to read the prior books other than for the sake of completeness. Still, that doesn't mean I might not visit those earlier books and get caught up on what I've been missing.