Books dealing with the g3 Queen's Indian What are the best repertoire or opening books, if any, advocating the g3 variation vs the Queen's Indian for White, in terms of analysis and verbal explanations of the main plans / ideas?
I will have to explore through some of the new (and older) literature on the Queen's Indian to give you better recommendations, but off the top of my head I recall at least 3:


Play the Queen's Indian by Andrew Greet: if I remember correctly the fianchetto variations are discussed somewhere at the end of his book. One plus about this book is that it's quite readable.
Starting Out: The Queen's Indian by John Emms: This is probably what you're looking for, there's an extensive study on the g3 variation (up to 70 pages almost). Also see his post here.
Queen's Indian Defence by Jacob Aagaard: I've heard good things about this one, but haven't read it myself, see chapter two. Apparently it contains numerous references to insightful games, for whatever variation that is covered in the book.


Finally, to browse through the known variations and played games, there are many websites that you can look through, but these two should get you started:


365chess
Queen's Indian (E15) page on chessgames