The book introduces and critically reviews conceptual and empirical issues surrounding the topic of smartphone addiction. Smartphone addiction has been proposed as a candidate psychiatric disorder characterised by disordered, problematic, uncontrolled use of one's phone or the content on it. There is now a literature of several thousand papers exploring the risks and consequences associated with smartphone addiction. This has led to calls for intervention in the media worldwide, including restrictions and bans on digital media. However, there are fundamental concerns about smartphone addiction and how it is defined, researched, and studied, which necessitates a pause for thought. This book explores several of these concerns: conceptualisation, measurement, methodology, and treatment, each requiring a comprehensive, integrated investigation. This multi-lens examination of the issues with smartphone addiction enables us to draw wide-reaching conclusions about the state of smartphone addiction and how these issues can be addressed. This is especially important in light of critical problems that are prevalent in behavioural sciences, such as concerns about the quality of measurement, the replication crisis, and the growing open science movement.