This is Activision, and a Spidey game, so obviously collectables are involved

...
However, this isn't that bad (I remember Spider-Man 2 collectables - ugh...). There are 700 comic pages all around the city, and just the city.
You do not have to deal with these things during missions in confined areas - there are other collectables in those areas for you to find

.
Anyway, there are two areas you will find these pages: either stationary on a surface (the ground, building perch, lamp post, etc) or floating around in the sky.
The best advice I can give is to pay attention. I found 99% of mine by simply noticing when the "R1 Comic Book Page" prompt came on screen. Then I would hit Web Rush (R1) and
usually the center cursor would default to the page.
Now, I know what you are thinking: "But if there are 700, then this could become a nightmare once you get 650 or so!" True, and those of you who played games like Spider-Man 2, Prototype, and other games with a ridiculous number of collectables are right with your concern.
However, I believe Activision is learning (maybe

). Once you hit 500 pages, the last 200 appear on your mini-map as yellow dots. As you swing around the city you will notice them pop up on your map as you get close to a respective page, so the daunting task of "finding every last one" becomes much less tedious.
If I missed anything please let me know in the comments section.