It's easy to read, easy to understand, very good graphics; Kuby is a very friendly book for new students, and for refreshing many concepts if you are very busy (and I bet you are!). I love it. But if you have more time available for reading, I would recommend Fundamental Immunology (Paul) and Cellular and Molecular Immunology by Abbas.
And try to keep up-to-date with new material on scientific magazines. See, in research you don't depend on books, that's only at the beginning or if you have to refresh some concepts. Once you have your knowledge, you will be reading papers on scientific magazines and less books. Many times, the concepts you have learned on books can change very fast. Science is a dynamic field, always changing.