There is no gold technical book, all gold gear is found in the SW isolated island village (airship only). The 'ultimate' technical book is found in the area past the blue tentacles.Where is the gold technical book?
Did I get the wrong ending?
One hit ko'd by the demon king and then came back full of darkness and destroyed his face
And congratulations for finishing the game with the "loss" ending. You may now enter NG+. It's possible to defeat him in a fresh NG, but you'll want all the allies you can get, the best gear in the game (all gotten from optional bosses), rank 5 ("Emperor" or "Sword Saint") crests, and maybe a couple thousand levels.