A few folks have asked about recommended reading on this topic. Here’s a list of some books you might be interested in. I haven’t read most of these, but they’re on my radar to check out.
Make It Stick
Learning to Fly
Facilitating with Ease
ISD from the Ground Up
The Six Disciplines of Breakthrough Learning
Basic Principles of Curriculum and Instruction
Evaluating Training Programs: The Four Levels
The Adult Learner (very academic, but tremendous overview of theory)
Lessons in e-Learning, Learning and Training
The Neuroscience of Adult Learning
If you read one of these or have other resources to recommend, please chime in!