André Klein Graded Readers
The André Klein Graded Readers can help build reading skills for German learners at different levels through fun, easily digestible stories. The books are structured to be accessible for learners, while teaching vocabulary in the context of phrases (rather than isolated words).
Lower-level beginners might like the Learning German With Stories And Pictures series or the Learn German With Less Text, More Fun series, both of which intersperse short sentences with numerous drawings depicting their meaning.
Upper-level beginners might prefer to start with the Dino lernt Deutsch (Dino Learns German) series, which uses simple vocabulary and repetition of related phrases for reinforcement. Intermediate learners can try the Baumgartner & Momsen detective series. Aschkalon, a fantasy adventure series, was written for advanced learners.
It seems fairly easy to follow the stories. The multiple-choice questions after each text help you gauge your understanding.
The glossaries tend to be formatted as large text blocks of German phrases and English definitions, which can be difficult to scan. In the Dino lernt Deutsch series, readers may find the pervasive boldfacing in the texts distracting.
For the amount of money and time invested, you can gain better reading comprehension, increase your German vocabulary, and build your confidence as a German learner — all in an entertaining and low-stress way.