Serial flicker.

I recently attended Thought Bubble, a comic convention in Leeds. I was stood talking with an illustrator flicking through one of his comic books when he told me to stop because that was the last in the series and I would ruin the ending for myself if I looked at the last few pages.
 It got me thinking about how I often have a tendency to do this with novels (and with comics because I'm an idiot) I have no idea why. But it struck me that if there were illustrations in it I could very well ruin the book for myself if they were explicit enough to tell me the story. Then again with a lot of illustrated YA books that I used to read I would purposefully do this just to see the illustrations and I guess in a way try to figure out where the story was going.
(I feel I'm in the difficult position where I'm such a visually aware person that I struggle to guess what the general population would do. I can't wait to see all the drawings but they might just read it normally.)

As in illustrator would you factor in the possibility someone (or even most people) may flick through the book before reading or even buying it? Would you make sure none of your illustrations were explicit of the story? To have an image of the main character with their head chopped off at the end of the book would surely be a huge risk.

I've looked at the idea that you could place an illustration too far forward in a narrative and thus change how you read it but I hadn't considered the freedom of the reader to look forward in the physical book itself.

 Is this a point down on the illustrated novel side or just something else that the illustrator need be wary of?

Chris Riddell