To crop and clean a douple page. 

There are of course multiple ways to use for cropping and cleaning a difficult page as this. All with their own advantages. What's here is the fastest way I know. Doing like this twists artwork a little bit if perspective crop is involved so I would call result of this example as medium quality.
If you want HQ, do copy&paste to new layers by transformed selections (Make selection. Then "Select>Transform Selection") or with rectangular crop.




I'm using "Demon Hunter Eton v4 p008" as example.
-http://kickthekitty.files.wordpress.com/2010/04/step-00.jpg

First make draw a crop area about right size.
-http://kickthekitty.files.wordpress.com/2010/04/step-01.jpg

Then rotate and stretch crop area to more or less cover the page.
-http://kickthekitty.files.wordpress.com/2010/04/step-02.jpg

If  just rotating didn't work, you need to use perspective. Enable perspective cropping.
-http://kickthekitty.files.wordpress.com/2010/04/step-03.jpg

You can now reshape crop area by moving it's corners.
-http://kickthekitty.files.wordpress.com/2010/04/step-04.jpg

Then crop. Perspective crop usually performs well. (If it doesn't and artwork get's twisted, you will just have to crop the hard way. Read from the hard way at the bottom of the page.)
-http://kickthekitty.files.wordpress.com/2010/04/step-05.jpg

Now copy cropped image. Do "step backward" twice (ctrl+alt+z) so that you get back to uncropped image. And paste (ctrl+v). You now have cropped page in a new layer.
-http://kickthekitty.files.wordpress.com/2010/04/step-06.jpg

Move cropped page aside and proceed to crop and paste other page same way.
-http://kickthekitty.files.wordpress.com/2010/04/step-07.jpg

Then turn background invisible so that it won't distract you. Or turn it to white or black if you prefer. As long as I can see edges of the cropped pages clearly.
-http://kickthekitty.files.wordpress.com/2010/04/step-08.jpg

Ups. They don't match! Perspective is a bit stupid so prepare to scale the pages to same size.
-http://kickthekitty.files.wordpress.com/2010/04/step-09.jpg

Make sure you have aspect ratio on!
-http://kickthekitty.files.wordpress.com/2010/04/step-10.jpg

Hmm. It seem we are missing some artwork.
-http://kickthekitty.files.wordpress.com/2010/04/step-11.jpg

We need a background. In this case black background is best.
-http://kickthekitty.files.wordpress.com/2010/04/step-12.jpg

Crop it.
-http://kickthekitty.files.wordpress.com/2010/04/step-13.jpg
Tadaa! Cropped like a pro.


- - - - -


Now let's clean this pic!
There's no need to keep pages in layers anymore. Flatten image. (It makes cutting easier.)
-http://kickthekitty.files.wordpress.com/2010/04/step-14.jpg

Level image. You could of course have leveled image before cropping too. I leveled this one with [80 1,23 225]. (If you wish to level some part of the image differently then rest, cut and paste it to new layer.)
-http://kickthekitty.files.wordpress.com/2010/04/step-15.jpg

Now get rid of the spine dirt. Switch to proper background color, select and cut (ctrl+x).
-http://kickthekitty.files.wordpress.com/2010/04/step-16.jpg

Just go wild... If it looks like trash or you feel image would be better without it then cut it away.
-http://kickthekitty.files.wordpress.com/2010/04/step-17.jpg

Time to save.
-http://kickthekitty.files.wordpress.com/2010/04/step-18.jpg

FINISHED!
-http://kickthekitty.files.wordpress.com/2010/04/demon-hunter-eton-v4-p008.png




Redraw. Do you wish to edit even further? 
Notice that what's described above is the easy and fast way.  As I said before, use of perspective crop will twist the image. So if you want to spent time and effort to redraw then you should use normal rotated rectangular crop instead of perspective or use selection to copy and rotate pages. Clean away what's not part of the page as in part 8, and then redraw (in this case) triangular spine:
http://kickthekitty.files.wordpress.com/2010/08/demon-hunter-eton-v4-p008triangle.jpg


Redrawing is basically easy. You use Photoshop clone tool to take artwork from elsewhere the page and paste it to empty place. Remember that "clone tool" can also copy artwork from different layer. So you can copy part of the page to new layer and rotate, flip or stretch it.
-http://kickthekitty.files.wordpress.com/2010/04/demon-hunter-eton-v4-p008-redraw.png
Nevertheless redrawing is usually time consuming. And requires some artist skills (which I lack as you can see from example pic).

- -

As for resize. If you wanna scanlate in the easy way, then leave picture so big that it won't need any filters for it's pixel textures. For Eton, minimum image size would therefore be around 2300px height.
-http://kickthekitty.files.wordpress.com/2010/04/demon-hunter-eton-v4-p008resize.png