Here is a non exhaustive list of books that I recommend on dog training and dog behavior in order to better understand your dog.
Planète Chien, from Joëlle Caverivière
The Culture Clash, from Jean Donaldson
Dogs are from Neptune, from Jean Donaldson
Don't Shoot the Dog!: The New Art of Teaching and Training, from Karen Pryor
When Pigs Fly!: Training Success with Impossible Dogs, from Jane Killion
Dominance, fact or fiction, from Barry Eaton