Design is a Job, written by Mike Monteiro. This is a relatively short book that gets you in the right mindset for client work. In the eyes of the author UI/UX is something so fundamental, that he doesn't feel like it should be separated out as an extra. Good UI/UX thinking permeates this book, and it's likely that you'll want to re-read it regularly.
Pro A great entry-level book
Design is a Job is a book that can be useful for designers of any professional level, but especially for those starting out in the field. This book contains practical and actionable tips for the designer mode of being, such as doing jobs that you find to be morally and ethically sound (otherwise you won't be proud of yourself or your work).