I like the idea of him disintegrating, but the transition from solid to particles feels very linear. I think having some larger clumps at the edges (which also move up) would work better, and then those clumps would break up into single-pixel particles.
Is the page meant to be inside of him, and the body around it disintegrates? If so, I think it reads quite well! It even looks like you have some particles coming off the page as it flies up, I think you should make those more visible and maybe trail from the page a little longer, as they look more like stragglers from the transformation than coming off the page.
If the page being inside him wasn't your goal, or if you're looking for alternatives ideas, how about having the particles gather towards the center and coalesce into the page?
How will this animation work when the character is in motion? Will the character's body just stop moving suddenly, or will you wait for it to stop before playing the animation? Since you have a static element (the book), I think this would look weird starting to play while the character is still in motion.