I've been writing and shooting funny films and videos for my entire life. I know exactly where the funny parts of my videos are because I can watch an audience and they'll tell me with a laugh. (or tweak things if I'm getting no response)

Recently I wrote a novel. I wasn't necessarily trying to be FUNNY...but I guess it just came out that way. (I was just shooting for 'merely amusing'.) Cut to a year later and now I'm getting reviews from people saying "this was a really funny book." Some people claimed they laughed out loud. The problem is I don't know WHERE it was funny. I've asked these people to tell me on what page and what paragraph WAS FUNNY. They're usually of no help. I typically get "I dunno...it was just funny."

Obviously not everything was funny...but I'm trying to zero in on what worked. Short of sitting next to a person and watching them read my entire book, I don't know how I'm supposed to get better at this. Include a high light marker with each copy?