Lauren Myracle's TTYL is a peek into the friendship between three 15-to-16-year-old girls in a typical 10th-grade milieu. The book is written as a series of IMs. That is, it is made up of Instant Messaging "chats" via computer (the title refers to the chat room abbreviation for "Talk To You Later"). The reader is eavesdropping on private conversations between the three main characters.
TTYL is written to appeal rather narrowly to young women near the age of 16; readers any significant distance from that demographic will find the book rather light and fluffy. The book is part of a series including TTFN ("Ta Ta For Now) and l8r g8r ("later, gator"). My review of TTYL will have to stand for the whole series, because I am NOT reading the others.
The book contains occasional strong language and some references to (but no outright descriptions of) sexual activity. Some alcohol use occurs, but no smoking or drug use. Actions have consequences, as when drinking leads to public embarrassment. One character, through naivete, gets herself into a potentially sexual situation, but her friends intervene in a way to prevent anything from happening.
Frankly, the material some might find objectionable is quite light in TTYL compared to that found in many other books marketed to the around-10th-grade age-group. Few parents who have actually read the book will object to their 15-year-old reading it.
In spite of its age-appropriateness, TTYL is frequently challenged. It appears on the American Library Association's list of Ten Most Frequently Challenged Books of 2008 and Ten Most Frequently Challenged Books of 2007, for rather unlikely reasons listed as "offensive language, sexually explicit, unsuited to age group". A superintendent actually removed the book from a middle school library in the Round Rock (Texas) school district, in spite of a review committee's recommendation that the book be retained.
It is clear that most book challengers never read the books they challenge.