I can't say I hated Dear Diary but I'm not a total convert like all the other reviewers here.
There are definitely some sections - particularly her middle and high school entries - where I felt like "OMG, that's EXACTLY how I was feeling at that age." And her updated commentary on some of those passages is really spot on and, in some cases, very funny. I also thought her description of her first time in rehab had some bittersweet, and in one case, hilarious, moments.
But on the other hand, as another reviewer mentions, I have a really hard time with her claim that she published the book to let girls know they aren't alone in what they might be going through. Nothing in her "update" commentary is particularly dissuading about drug use... or even tormenting your friends, for that matter. She seems to have taken thinly veiled delight in the fact that, although her middle school friends tormented and ousted her, they were also tormented and ousted by each other.
While she is a decent writer, and the entries aren't quite as boring as one reviewer would have you believe, I was ultimately left with the feeling that I really don't like or care about Leslie that much. She may be sober now and she may have gone through the school of hard knocks like a real champ but she still comes across like an immature, spoiled upper middle class Gen-Xer. Ironically, she pretty much admits this.