I've read her The Princess Diaries series as well as The Mediator series.
The new series is more in the range of adult novels but just as funny as her other series ^^
The first book is called Size 12 Is Not Fat (German: Darf's ein bisschen mehr sein?)
At 28, former teen-pop-star Heather Wells feels as though she has lost everything: her family and fortune (her mom fled the country with Heather's earnings), her recording contract, her slender waistline, and her fiance, Jordan, a philandering, boy-band singer. Then Jordan's brother, Cooper, a dreamy private investigator and family black sheep, offers Heather room and board in exchange for clerical work, and she finds an additional job as a residence-hall director at a nearby Greenwich Village university. After several female students turn up dead at the dorm, Heather takes on her own stealthy investigation and finds herself the target of the killer.
The second book is called Size 14 Is Not Fat Either
A cheerleader in Heather's dorm turns up dead—or, at least her head turns up, stewed almost beyond recognition in a cafeteria pot. Lindsay Combs was bubbly and popular, but as Heather digs deeper, she learns that Lindsay wasn't all sweetness and light. She slept around and was involved with obnoxious fraternity boys who made pin money dealing drugs. If solving Lindsay's murder isn't enough to keep Heather busy, her father, recently released after a 20-year prison sentence, shows up on her doorstep, looking for a renewed relationship and a place to stay.
A thrid book will be released this December or in January 2008.
Even though the novels are not without flaws (some things are too predictable and the suspects could be a little more suspect-ish), I really enjoyed reading them. Heather is such a cute and funny klutz, you just have to like her ♥ Maybe you enjoy them, too ^^