This really isn't that hard. Here's the step-by-step for creating a new chapter version.
1. Go to Your Porftolio.
2. Click the title you want to add a new version to.
3. Go to the Content sub-tab.
4. Click the add chapter button
5. Fill in this chapter and increment the version to whatever number you want.
6. Click Save and Publish
7. Go to the Publish page and publish the new chapter.
At that point, you can keep the old version active, or not. You do not change the version number on the old version, this will overwrite the old version. Instead, you have the option of creating an entirely new version and keeping it within the book. There is no need to create a new book, etc. This will bring it to the top of the list and it will also preserve the old version should you want to refer to it, etc. This is a true version system. The old republish system was not a version system at all.
Try it, you might like it.