Gestalt Laws are most often referenced as a basis for what we know about how humans visually perceive the organization of things, or perceptual proximity.
Some known ways that perceptual proximity can be achieved are,
- Spatial proximity - things closer together will be perceived as a group.
- Similarity - things that are similar in size, shape, or color are perceived to be in a group.
- Connectedness - things that are aligned or linked together appear to be in a group.
- Closure - our minds fill in missing information to create a whole. So, things will appear to be grouped if they create an object.
You will not find a definitive book because as @Rahul and @Splog have pointed out, Gestalt psychology is more of a branch of thought.
There's a nice online summary of Gestalt Principles at Scholarpedia.
If you would like to learn more, pick up a copy of Engineering Psychology and Human Performance. Chapter 3 on Attention in Perception and Display Space and Chapter 4 on Spatial Displays will give you a thorough overview of the theories behind visual perception.