These are great books that will help you better understand your dog & how to teach them.
If you were to only read two books from this list, my top recommendations are
Canine Enrichment for the Real World and Doggie Language!
Canine Enrichment for the Real World by Allie Bender & Emily Strong
Doggie Language: A Dog Lover's Guide to Understanding Your Best Friend by Lili Chin
Puppy Socialization: What It Is and How to Do It by Marge Rogers & Eileen Anderson
Control Unleashed - Creating A Focused and Confident Dog by Leslie McDevitt
Control Unleashed - The Puppy Program by Leslie McDevitt
Plenty In Life Is Free - Reflections On Dogs, Training and Finding Grace by Kathy Sdao
Meet Your Dog: the Game-Changing Guide to Understanding Your Dog's Behavior by Kim Brophey
Love Has No Age Limit - Welcoming An Adopted Dog Into Your Home by Patricia McConnell & Karen London
Behavior Adjustment Training 2.0: New Practical Techniques for Fear, Frustration, and Aggression in Dogs by Grisha Stewart
Hunting Together: Harnessing Predatory Chasing in Family Dogs through Motivation-Based Training (Predation Substitute Training) by Simone Mueller
Rocket Recall: Unleash Your Dog's Desire to Return to You through Motivation-Based Training (Predation Substitute Training) by Simone Mueller
Don't Eat That: Force-Free Food Avoidance Training for Dogs who Love to Scavenge by Simone Mueller, Charlotte Garner & Päivi Kokko (Illustrator)
Be Right Back!: How To Overcome Your Dog's Separation Anxiety And Regain Your Freedom by Julie Naismith
Be Right Back! Puppy Separation Anxiety Edition: Your simple step-by-step guide to raising an easy-going, independent, happy-home-alone puppy by Julie Naismith
Separation Anxiety in Dogs: Next Generation Treatment Protocols and Practices by Malena DeMartini
Mine! - A Practical Guide To Resource Guarding In Dogs by Jean Donaldson
The Other End Of The Leash - Why We Do What We Do Around Dogs by Patricia McConnell
The Midnight Dog Walkers: Positive Training and Practical Advice for Living with Reactive and Aggressive Dogs by Annie Phenix