Italian vs Queen's Gambit

The December 2016 issue of Chess lists the top twenty openings compiled from a list of 2895 October games where both players were rated over 2400 Elo. One can not take position on this list too seriously because it is greatly influenced by how the openings are grouped. For example, all the Retis are grouped together, while English is separated into 1 ... c5, 1 ... e5, etc. Nevertheless, for what it is worth, one of the list entries is: 55 Italian games
The January 2017 issue only lists the top ten openings compiled from a list of 1701 November games, so I do not know if the Italian game managed to retain its place in the top twenty. The January top ten list does include 79 King's Indians, 64 Slavs, 59 Declined Queen's Gambits, 45 Nimzo-Indians, and 43 Queen's Indians, so it seems like a good guess that the Queen's Gambit is more popular with the over-2400 crowd. However, in the most recent issue of New in Chess, GM Anish Giri remarked that the Italian "has been very trendy recently".
A number of recent books have advocated the Italian game:
A SIMPLE CHESS OPENING REPERTOIRE FOR WHITE by Sam Collins
http://www.gambitbooks.com/pdfs/A_Simple_Chess_Opening_Repertoire_for_White.pdf
My First Chess Opening Repertoire for White by Vincent Moret
https://www.newinchess.com/Shop/Images/Pdfs/9033.pdf
Winning with the Slow (but Venomous!) Italian by Karsten Müller and Georgios Souleidis
https://www.newinchess.com/Shop/Images/Pdfs/9037.pdf
For the Queen's Gambit,
First Steps: The Queen's Gambit by Andrew Martin (2016) or
Starting Out: Queen's Gambit Declined by Neil McDonald (2006)
https://web.archive.org/web/20140627005627/http://www.chesscafe.com/text/hansen93.pdf
might serve as a general introduction. We have often seen recommendation of the somewhat older book, Queen's Gambit Declined by Matthew Sadler (2000).
https://web.archive.org/web/20140708234438/http://www.chesscafe.com/text/hansen15.txt
A few years ago, there were a number of books with advice for White:
A Strategic Chess Opening Repertoire for White by IM John Watson (2012),
https://web.archive.org/web/20140627105428/http://www.chesscafe.com/text/hansen161.pdf
http://www.gambitbooks.com/pdfs/A_Strategic_Chess_Opening_Repertoire_for_White.pdf
Playing 1.d4: The Queen's Gambit by Lars Schandorff (2012),
https://web.archive.org/web/20140626221508/http://www.chesscafe.com/text/hansen162.pdf
http://www.qualitychess.co.uk/ebooks/Playing1d4QueensGambitexcerpt.pdf
The Kaufman Repertoire for Black & White by GM Larry Kaufman (2012),
https://web.archive.org/web/20140626221508/http://www.chesscafe.com/text/hansen162.pdf
https://www.newinchess.com/Shop/Images/Pdfs/955.pdf
A practical repertoire with 1.d4 and 2.c4 Volume 1 by Alexei Kornev,
http://reviews.dailychess.org/a-practical-repertoire-with-1-d4-and-2-c4-the-complete-queens-gambit-volume-1-by-alexei-kornev-chess-stars-2013-304-pages/
https://www.newinchess.com/Shop/Images/Pdfs/7288.pdf
and A Cunning Chess Opening Repertoire for White by Graham Burgess (2013).
http://theweekinchess.com/john-watson-reviews/john-watson-book-review-110-repertoires-in-the-age-of-carlsen
http://www.gambitbooks.com/pdfs/A_Cunning_Chess_Opening_Repertoire_for_White.pdf
I think Watson, Schandorff, Kornev, and Kaufman advocated 1 d4 d5 2 c4 e6 3 Nc3 Nf6 4 cxd5 exd5 5 Bg5, while Burgess advocated 1 d4 d5 2 Nf3 Nf6 3 c4 e6 4 Nc3 Be7 5 Bf4.
If the Catalan is your interest, perhaps the most recent book help is to be found in Grandmaster Repertoire 1A - The Catalan by Boris Avrukh
http://www.qualitychess.co.uk/ebooks/GM1A-Catalan-excerpt.pdf
and Grandmaster Repertoire 1B - The Queen's Gambit by Boris Avrukh.
http://www.qualitychess.co.uk/ebooks/1BTheQueensGambit-excerpt.pdf
Not sure what the focus is for the 2016 books, The Queen's Gambit by Damian Lemos and First Steps: The Queen's Gambit by Andrew Martin.
Advice for Black can be found in Declining the Queen's Gambit by John Cox (2011).
https://web.archive.org/web/20140626233841/http://www.chesscafe.com/text/hansen149.pdf