As manners and etiquettes are also an important part of Judaism, are there websites or online books in English that discusses in detail all the important derech eretz laws?
I think it is difficult to discuss ALL the laws as derech eretz is both general and situational. We learn the general principles and see some of the application, but then have to apply those guiding ideas to the specifics of our daily experiences.
Some websites which might start you on the right path include https://www.chabad.org/library/article_cdo/aid/3469552/jewish/What-Is-Derech-Eretz.htm http://www.beverlyhillschabad.com/halacha/halacha-manners.htm http://www.chinuch.org/topic/1/Derech-Eretz http://halachayomit.co.il/en/default.aspx?HalachaID=2962
here are some practical applications relevamt to one context https://www.icja.org/about-icja/student-expectations/derech-eretz-policy/