I admit it - I am a big fan of The Sisterhood of the Traveling Pants series. I just read the fourth and last book, however, and was exceptionally disappointed. I wasn't terribly impressed by the story line, and felt that the characters remained fairly static, but that isn't my main complaint. What bothered me was the fact that the characters generally took a moral nosedive. Amid the masses of catty fiction for teenage girls (think of popular series like Gossip Girl, The Clique and It Girl), it's nice to find something that I wouldn't actually mind my younger sister reading. While the first three Sisterhood books weren't all sweetness and light, the characters made choices, faced the consequences of them, and generally learned some important lessons. The books didn't necessarily preach against drinking, premarital sex, etc., but they steered far clear of glorifying them, something I greatly appreciated. You may find my view stuffy or prudish, but I believe kids don't need to be thinking about that sort of thing, and as for the "growing with your audience" argument, do those topics really make the story any more mature? Personally, those aren't my criteria for maturity. But I digress. The fourth Sisterhood book slipped off its moral high ground and left the characters making some fairly suspect choices with less than severe repercussions. The general message I took away was that growing up means losing your inhibitions. In small doses, that's a fine message, but it really ought to come with the caveat that some inhibitions are there for a reason. That's my stand on the matter, anyway. And you ought to read the book, if only to round out the series.
As an aside, no offense meant to anybody who reads catty teen fiction. It's pure brain candy, and I certainly indulge in it myself. It's only a problem when that sort of thing is all that younger girls are reading, without the realization that it's trash. There's no reason not to eat candy, as long as you don't go around thinking it's broccoli (or insert healthy food of your preference here).