1. 100 Things Every Designer Needs to Know About People
By: Susan M Weinschenk, Ph.D

In order to continue to develop your skills as a user experience designer, you ought to further your understanding of the user that will be interacting with the product.
In order to understand the user you must understand people. There are a number of fundamental concepts in the field of psychology that govern the decisions that people make.
As such, a surface-level understanding of psychology is a requirement for any UX designer. This book was written by a behavioral psychologist who has been working with UX design for decades.
100 Things Every Designer Needs to Know About People delivers great insight, using psychological science, research, and practical examples to examine and explain why people do things the way they do.
2. Smashing UX Design
By: Jesmond Allen & James Chudley

Smashing UX Design is a user experience reference manual that gives readers an overview of what UX really is, while taking a deeper look into the most commonly used tools and techniques.
The reference manual is filled to the brim with usability case studies, how-to guides, and checklists. From user research to wireframing, this useful guide showcases a case study for each and every aspect of UX Design.
3. Mobile Usability
By: Jakob Nielsen & Raluca Budiu

In this day and age, if your website isn’t mobile-friendly, it doesn’t stand a chance. Statistically—and a simple Google search will confirm this—mobile web users are far more likely to bounce from your page if it isn’t optimised for their devices.
And if it’s absolutely essential that a website be responsive and mobile-friendly, then it’s implicitly essential that every UX Designer understands the principles and best practices of mobile UX.
That’s where Mobile Usability comes into play. For the budding UX designer, Nielsen and Budiu’s in depth mobile usability guidelines are irreplaceable.
4. Lean UX: Applying Lean Principles to Improve User Experience
By: Jeff Gothelf

In his book, Jeff Gothelf applies the principles of ‘lean’ to UX.
Some of the core principles are:
- Generate as many options as possible
- Prototype and fail as quickly as possible
- Improve and build upon your work consistently
- Recognize hypotheses, then validate them
Lean UX: Applying Lean Principles to Improve User Experience helps the budding UX Designer recognize the benefits of moving toward a ‘lean’ approach, and describes how to build better products through collaborative techniques.
Through the use of case studies, rational advice and theory, Gothelf has managed to create an excellent critique of what an efficient UX process ought to look like.
5. Usable Usability
By: Eric Reiss

Eric Reiss is a well known UX expert. This book is a guide designed to help UX designers identify and fix some of the more common (in addition to some of the more complex) usability issues.
Usable Usability gives the reader an in-depth explanation of what usability is and why it is important, while providing a large range of usability concepts to its readers.
The book, which is split into two different parts—”Ease of Use” and “Elegance and Clarity”—is not only useful for UX designers, but is also a very popular reference among developers too.