On the book reader page you can highlight important sections of content and add your own notes to enhance your learning.

Go to Highlights from Your O´Reilly menu on the Home Page. 

To the left, there is a list of the books where you have added highlights and notes.

You can see notes you have added.

You can export your highlights and notes to a spreadsheet, which includes titles and links. This will help creating citations.

To edit, just click the text snippet and you will be taken back to the book reader page where highlights and notes can be changed or removed.