Operating Systems: Internals and Design Principles, 9/e Paperback – January 1, 2018

Just an FYI, this book won't teach you how to "use" an operating system, but rather all the parts that make up a modern OS. This book is an absolute must to read before becoming a decent programmer. You don't need to memorize the whole book, just be aware of the concepts contained within and have a good mental model of it.