Graded readers are reading books that contain language adjusted to the level of the learner rather than authentic language.

Example
Many ELT published produce graded readers for a wide range of levels.

In the classroom
Graded readers can help learners build their confidence in reading, and they can make a useful addition to exposure of authentic reading texts, even at very low levels. Activities with graded readers include imagining and creating the past lives of characters, dramatizing key scenes, and writing letters to the author.