Catchbook basic functionality is shown in 5 videos in this post. This includes, how to draw accurate curves, how to turn the active stylus mode on and off, how to select objects as well as other basic functions such as Scribble Delete and Pen Selection.
Drawing Ink and Curves in Catchbook using both finger and stylus:
Using Scribble to delete and trim:
Selecting ink, curves and images with Tap and Lasso:
Zooming and Panning (Hint: Double tap fits the page):