If you have a scanner or access to one, placing your Gor books on disk does have its perks.
Though it is hard to read off the computer screen, when doing research it is hard to beat for pulling up the book and running a search through your editor. When you find what you are looking for, it makes it easier to then return to your book and highlight the quote you feel is important.
For those who go the highlighter route, I recommend using four different colored highlighters.
Use a different color for Men's quotes... Women's quotes... slave's quotes, and one color for general quotes.
In the margins it is also handy to cross reference with the other books by sticking to the highlighted system. Highlight the ref the same and just jot down the book and page beside your books original quote.