A new white paper for the Oracle Optimizer is now available. Just go to the Query Optimization page in OTN and click the Optimizer with Oracle Database 12c link.
I've kept the content and format close to the way Maria organized it, so it will be familiar to you if you've read previous versions. The main difference is that I've reduced the number of scripts in the text to keep the paper down to about 30 pages, otherise it's too easy to hit 40+. As an alternative, I upload examples to GitHub.
Post comments to this blog if you want to give me feedback on the white paper's content. If you want more examples, let me know and I'll add suggestions to my to-do list. Of course, I intend to post more entries here (and scripts to GitHub) to cover things in more detail anyway.
Finally, in OTN you'll see a bunch of other white papers referenced in the Optimizer page. At the time of writing, these are for Oracle Database 12c Release 1. Needless to say, updates to those are on the way.