(Note this script is a work in progress. I haven't put any effort into a command line interface, so you may have to edit the file to work for you).
Safari Books Online lets you highlight book passages and attach notes to those passages.
It also lets you download all of your highlights and notes as a CSV file.
This script will parse the CSV file from Safari Books Online and output a CSV file you can import into Anki. Each line of the file will be a new card.
For an example on importing to Anki see this post on StackExchange.
One strategy may be: when you find something in a book on SBO you want to convert into a card just highlight the passage, create a new note, and your "note" should be the question, and the highlighted passage is the answer.
I use a custom card format in Anki that has Front, Back, and Note. In the Note field I put the URL to the passage I highlighted.