My bone broth dehydrated overnight to the point where the meat and veggies were brown and dry on top. I've added water back in, but was wondering if it is any good. Perhaps I'll have a batch that tastes different.
The temperature will have been high enough to be safe, so don't worry.
What you'll get is a darker, quite tasty stock. It's not suitable for everything (it's likely to be cloudy as well as dark) but can be very good. When I first got my new slow cooker it tended to do this, because it runs a little hotter than my old one. Running it on low instead of high (starting with boiling liquid) solved that.
You can also use the concentrated stock you've made, just remember to use much less than you would of normal stock.
No need to worry.
The more water evaporates, the thicker your broth becomes, until you get kind of to Demi-glace. Very tasty and can be used as concentrated stock to enhance a lot of dishes. I usually refrigerate this as ice-cubes for easy use.
Of course, if you do this intentionally, you would siphon off the broth and reduce in a separate pot. You can even pull a stock several times from your bones, adding to result together in your reduction.