I have several books, try to stick with ones within the past few years, since info changes so often. I've read all I can find. I subscribe to Bird Talk magazine, mostly for the pictures.
For training, my favorite book is Getting Started Clicker Training For Birds by Melinda Johnson or Good Bird Inc website & books. I also have a book called The Click That Does the Trick, but I don't like this one as much.
I don't like most online info sources because they are mostly opinion, rumor, or outdated. I prefer info straight from reputable Avian Vets or Trainers.