Books on Nimzo-Indian
Possibly of interest:
Nimzo and Bogo Indian by Christof Sielecki
http://www.jeremysilman.com/shop/pc/Nimzo-and-Bogo-Indian-The-76p3910.htm
https://www.newinchess.com/media/wysiwyg/product_pdf/7361.pdf
Starting Out: The Queen's Indian by John Emms (2004)
https://web.archive.org/web/20140627042117/http://www.chesscafe.com/text/hansen68.pdf
Maybe also consider:
Starting Out: The Nimzo-Indian by Chris Ward (2002)
https://web.archive.org/web/20140627075509/http://www.chesscafe.com/text/hansen42.pdf
The Nimzo-Indian: Move by Move
https://web.archive.org/web/20140626165831/http://www.chesscafe.com/text/hansen155.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/7030.pdf