Business resources
The Lean Startup
How Today's Entrepreneurs Use Continuous Innovation to Create Radically Successful Businesses - by Eric Ries
This book will help you understand how to develop and launch a new product using lean methodologies, which will be useful for your 'on the way' app idea.
Hooked
How to Build Habit-Forming Products - by Nir Eyal
This book will teach you how to create products that people will not only use but will also become a routine part of their lives, which is essential for the success of an app like yours.
Traction
How Any Startup Can Achieve Explosive Customer Growth - by Gabriel Weinberg, Justin Mares
This book will provide you with strategies and tactics for acquiring new customers and growing your user base, which is vital for the success of your 'on the way' app.