Possibly helpful:
Starting Out: Ruy Lopez by John Shaw (2003)
https://web.archive.org/web/20140627024240/http://www.chesscafe.com/text/hansen53.pdf
A Spanish Repertoire for Black by Mihail Marin (2007)
https://web.archive.org/web/20140626195205/http://www.chesscafe.com/text/hansen102.pdf
The Berlin Defence by Igor Lysyj & Roman Ovetchkin (2012)
https://web.archive.org/web/20140627104938/http://www.chesscafe.com/text/hansen159.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/7076.pdf
The Ruy Lopez: A Guide for Black by Sverre Johnsen and Leif Johannessen (2007)
https://web.archive.org/web/20140627023224/http://www.chesscafe.com/text/hansen94.pdf
Bologan's Ruy Lopez for Black by Victor Bologan (2015)
http://www.sjakkbutikken.no/produkter/bologans-ruy-lopez-for-black/
https://www.newinchess.com/media/wysiwyg/product_pdf/9016.pdf
Play 1 e4 e5! by Nigel Davies (2006)
https://web.archive.org/web/20140626201436/http://www.chesscafe.com/text/hansen80.pdf
https://web.archive.org/web/20140627083715/http://www.chesscafe.com/text/hansen98.pdf
https://web.archive.org/web/20140627031152/http://www.chesscafe.com/text/ebcafe10.pdf
The Berlin Wall by John Cox (2008)
https://web.archive.org/web/20140627050257/http://www.chesscafe.com/text/hansen115.pdf
Attacking the Spanish by Sabino Brunello (2009)
https://web.archive.org/web/20140627105306/http://www.chesscafe.com/text/hansen124.pdf
http://www.qualitychess.co.uk/ebooks/Attacking_the_Spanish_excerpt.pdf
The Ruy Lopez Revisited by Ivan Sokolov (2009)
http://dev.jeremysilman.com/shop/pc/Ruy-Lopez-Revisited-The-p3765.htm
https://www.newinchess.com/media/wysiwyg/product_pdf/931.pdf
Fighting the Ruy Lopez by Milos Pavlovic (2009)
https://web.archive.org/web/20140627105306/http://www.chesscafe.com/text/hansen124.pdf
Slay the Spanish by Timothy Taylor (2011)
https://web.archive.org/web/20140627040230/http://www.chesscafe.com/text/hansen146.pdf
The Kaufman Repertoire for Black & White by Larry Kaufman (2012)
https://web.archive.org/web/20140626221508/http://www.chesscafe.com/text/hansen162.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/955.pdf
Grandmaster Repertoire 13 – The Open Spanish by V. Mikhalevski (2013)
http://reviews.dailychess.org/grandmaster-repertoire-13-the-open-spanish-qualitychess-by-v-mikhalevski/
http://www.qualitychess.co.uk/ebooks/GM13-excerpt.pdf
Anti-Spanish. The Cozio Defence by Alexey Dreev (2014)
Playing 1.e4 e5 - A Classical Repertoire by Nikolaos Ntirlis (2016)
https://www.newinchess.com/media/wysiwyg/product_pdf/7572.pdf
The Spanish Main Road by Evgeny Solozhenkin (2016)
https://www.newinchess.com/media/wysiwyg/product_pdf/7595.pdf
The Zaitsev System by Alexey Kuzmin
https://www.newinchess.com/media/wysiwyg/product_pdf/9036.pdf
The Berlin Defence Unraveled
https://www.newinchess.com/media/wysiwyg/product_pdf/9048.pdf
MY SECRETS IN THE RUY LOPEZ by Lajos Portisch
http://www.gambitbooks.com/pdfs/My_Secrets_in_the_Ruy_Lopez.pdf
In the last 8 games I played in the black side of the ruy lopez, I sucumbed to a kingside attack in all of them.
I've heard the ruy lopez was the opening where white has the bigger and more lasting advantage of chess, but I didn't expect it to be this much. I'm thinking about adopting the french or the classical sicilian and let the ruy to when my defense technique increases.
What opening doesn't need a too refined defense technique as black ?
Sugestions ?