Baumgartner & Momsen

This series is designed for intermediate learners starting around the B1/2 level. If you already understand German around familiar topics of daily life, aim to broaden your understanding across more complex topics (both concrete and abstract), and delve into more specialized vocabulary and idioms, these books are designed for you.

While the language itself doesn't necessarily get more difficult across the 5 episodes, the characters and the criminal cases are becoming increasingly more complex and involved as you read on.

For most learners we'd recommend to start with the first book Mord am Morgen which introduces the main protagonists and is also the shortest volume in the series. However, since each book deals with one specific case and tells a self-contained story, you can read these books in whichever order you prefer.