Are Captivate 8 and 9 almost identical?

Thank you both!

However you LEARN how to use Captivate, I would suggest that sooner or later what you REALLY need is a troubleshooting book.

Are you wasting too many hours troubleshooting annoying issues in Adobe Captivate? | Infosemantics Pty Ltd

There are significant differences between the two versions. Due to the frequency of releases (yearly) it is very difficult for authors to keep up with books. Personally, I find most books very superficial probably for the same reason: hurry to write and publish. That leads often to 'overlooking' the new features, to avoid exploring in depth what those changes mean; I'm often amazed when I read some training schedules, and see description of work flows that are certainly not up to date to say it very politely. I never bought a book, nor took any training. 

I know this is not helping you. I would recommend looking at video tutorials, blogs. Do not trust the Help documentation, except for the new features because the rest is almost not updated and contains still many references to older versions (not CP8 but much older ones).

New features can be found easily: Adobe Captivate Help | What's New in Adobe Captivate 9

Have a look at the included video tutorials coming with Captivate, play around with the example files, look at YouTube for other tutorials.

But even that page is not complete at all. They forgot some aspects. Users like me blogged about Captivate 9. Multistates, SVG import, improvements to responsive projects, greatly improved work flow for Effects, intelligent naming, improved Quizzing (knowledge slides, new Preview buttons), etc.