The word "guys" isn't so gendered in 2017 as it might have been 50 years ago. Far more importantly, though, gendered advertisements have had thousands of years of success. Don't insult or belittle any demographic, but keep in mind that it's entirely possible that many different sales pages targeting different demographics is the long-term solution.
For a first trial though, I'd narrow to a laser tight focus and pick one person you believe the book will most serve and write all your copy as if you were talking only to that one person. After you get uptake, expand.
For a first trial though, I'd narrow to a laser tight focus and pick one person you believe the book will most serve and write all your copy as if you were talking only to that one person. After you get uptake, expand.