15 minutes is a great attention span!! My son has about 6-10 minutes, and we have successfully gone through Outdoor Secrets and are most of the way through Pond and Stream. I would highly recommend Outdoor Secrets – it is soooooo interesting! The companion guide is great, too, as it suggests nature journal entries and extra picture books relating to the topic of each chapter. We are enjoying the Pond and Stream companion guide, too, with its picture books, nature studies, short video clips, etc. But we found it best to go through it at a quicker pace than the companion guide suggests. I still think Outdoor Secrets is an amazing place to start!!