Tara I agree Sky! I'd be a little iffy on a 12 year old. Maybe 13-14 minimum and 13 is questionable. Anyone who starts the series, of course will want to finish it so that's why I'd recommend the higher age bracket. It's very heavy in terms of making out. Anything that goes further is quickly passed and written as an assumption. But make out sessions are very detailed-not really ever including...body parts that we won't mention. But none the less quite steamy. When it comes to profanity-kids at early ages hear it all the time so that does little to sway my age recommendation when you're already speaking of middle school anyhow. I have read the entire series and cannot say that the last book greatly increased in sexual content. Maybe a tad but not enough to change my age recommendation.
Sky I know lot's of people have different ideas on what is and isn't appropriate so I'll just say that there is excessive swearing, intense kissing scenes, and mild sexual content. I have heard the third book in the series isn't appropriate though.