When you read a koob, there are a number of available features that allow you to:
Scroll the chapter from top to bottom / Scroll the chapters from left to right.
Enlarge/shrink the font size (1).
Switch to night mode (2).
Access audio (3).
View the table of contents and jump to a chapter directly from the table of contents (4).
Highlight a passage (see Highlights).
On the last page of the koob, click on "Finish" to put it in the "koobs read" category of the library.