That's an excellent question! Essentially, it is you, the author, taking over an event that you were either invited to, or hosting, and for that hour you are given, it's a chance to showcase your book(s) to new readers, and network with other authors. Here's a link that I read that explains it so much better than I can, and even tells you how to do one. I've had some "success" with takeovers, but it all depends on what you use to measure your successes. I want new likes/followers for my journey so when my second or third books come out, I'll have new readers. I'm doing this all out of order, I know. But, I'm gaining new faces, and new experiences for each one. Those are my successes. So, celebrate what you will! Join them, they're fun!! If you want to visit and see what in the heck I'm talking about, just click on a #fbevents and it'll take you to that event page.
I drink too much coffee, read too many books, and in between raising miracle babies, I find time to write.