This has happened twice with 1803 (I think). The first time, it seemed to successfully install, but right after, I updated Advanced System Care and when the computer restarted, I got the black screen with the rotating circle. (I can't be sure if 1803 or the ASC update was the cause.) My Win 10 recovery USB would not work, but I finally got my computer's built-in recovery utility to restore the computer to Win 7.
I upgraded back to Win 10, made a new recovery USB and tried the 1803 build again (I guess I'm a sucker). Again, it seemed to install OK, but upon restart same black screen and rotating circle. This time, however, the recovery media did work, so it wasn't as big a deal to get everything back to the way it was.
Third time is the charm, I guess. 1803 installed with no problems a couple of days ago, and everything is running fine. I don't know what the difference was this time.
I do have an SSD; I didn't know about this issue until reading this thread.
It might be a good idea to delay updating for the time being.