There are many books talking about UX/UI design, but most of them are quite abstract and do not tell you, when exactly, on which stage of your software development process to apply the knowledge they present. This often leads to a typical mistake done by developers, that I've seen in too many projects, when UI design is considered at later stages of the project, when they are starting coding the UI and all the backend is already done. Because of that, the process is equally important and needs some of your attention.
To achieve really good results in UX design, to do it at the right time, I'd recommend to start not from the books, but from the interaction design specialization on Coursera at https://en.coursera.org/specializations/interaction-design or you can take just intro - https://en.coursera.org/learn/human-computer-interaction. You can take the courses for free and they'll give you the necessary mindset and understanding of process. You'll find that product design actually starts from UX, not ends with it and it defines the necessary requirements framework for the system architecture, which you can use later in combination with BDD/DDD. After that course you can start reading the books (Steve Krug, Don Norman, Alan Cooper, indeed!) and platform guidelines (my favorites are for Google Material Design and Microsoft's Modern UI).
It will be great if someone here recommends some books or articles about UX design process and integration of it into popular agile methodologies.