If your child is struggling with anxiety or has been diagnosed with an anxiety disorder, I highly recommend What to Do When You Worry Too Much: A Kid's Guide to Overcoming Anxiety. This is a wonderful book to read with your child, which explains what anxiety is, how it works, and has great strategies. This book is a must have.
For children who have trouble managing their anger, What to Do When Your Temper Flares: A Kid's Guide to Overcoming Anger is fantastic. It is from the same series as the one mentioned above. Also within the series and highly recommended are: What to Do When You Grumble Too Much: A Kid's Guide to Overcoming Negativity; What to Do When Your Brain Gets Stuck: A Kid's Guide to Overcoming OCD; and What to Do When It's Not Fair: A Kid's Guide to Overcoming Envy and Jealousy.
If your child or teen is struggling with ADHD, I recommend Late, Lost, and Unprepared: A Parents' Guide to Helping Children with Executive Functioning. This book is helpful in explaining what executive functions are, how weaknesses in this area impact your child's academic performance, and strategies for what parents can do to help.
Get Out of Your Mind and Into Your Life for Teens: A Guide to Living an Extraordinary Life is a self-help workbook that teaches teens mindfulness and coping strategies. It utilizes Acceptance and Commitment Therapy (ACT), which is an evidence-based intervention. This book is helpful for those struggling with mood issues.
For any adult struggling with managing anxiety, stress, or depression, I highly recommend 8 Minute Meditation: Quiet Your Mind. Change Your Life. I've recommended this previously for insomnia but cannot say enough about how valuable the information in this book is for learning the necessary skills to quiet the mind.
Exercise for Mood and Anxiety: Proven Strategies for Overcoming Depression and Enhancing Well-Being provides great information on the benefits of exercise, which will encourage you to get out there and move around. It also has great work sheets and strategies.
Acceptance and Commitment Therapy (ACT) is a beneficial intervention that incorporates mindfulness with cognitive strategies. Get Out of Your Mind and Into Your Life: The New Acceptance and Commitment Therapy is a self-help workbook with great exercises and strategies. This book is helpful for those learning to manage anxiety, mood issues, or attention and concentration problems.