If you can find a dog from a rescue group where the dogs are cared at a foster homes, then you can ask the foster parents of the dog's disposition.

Some shelters do have volunteers who spend play time with the dogs and would have some insight into the dogs disposition. So do ask.

And I totally agree with read the dog and not a book.

My neighbor down in Los Angeles had a female pit bull dropped off in his lap. He wasn't really looking to take care of a dog but he ended up with the dog. And that pit bull was the gentlest and friendliest dog I've ever seen. He did take the dog to a park and she didn't show any aggression toward other female or male dogs. I was pretty amazed at her calm disposition. So do read the dog and not a book.

I also knew someone with a besinji. He was a feral and domesticated. He wasn't socialized and definitely very hostile toward other dogs. Owner had his set of issues too and it didn't help the dogs disposition. I think with proper training and care, that bisenji could have gotten over his emotional trauma.

So find out about the history of the dog if possible and talk with the foster parents.