If you have a printed book that you want quickly turned into an e-book, you can follow these steps:
1. photograph the book, two pages at a time
Take a camera, go to a bright enough place and take a snapshots of your book, two pages at a time. You can also scan them with a scanner, which will produce a better quality, but photographing may be several times quicker.
2. copy the images from the memory card to a temporary directory
3. check the image orientation
Manually check if the rotation of each image is horizontal (pages oriented left-right as opposed to top-bottom). Fix where needed.
4. install imagemagick
sudo apt-get install imagemagick
5. split the images
convert "*.JPG" -crop 50%x100% +repage "page_%d.JPG"
to split images with sharpening and normalizing (enhancing the contrast) at the same time:
convert "*.JPG" -normalize -unsharp 0x1 -crop 50%x100% +repage "page_%03d.JPG"
%03d part says that the counter will always be three digits long with trailing zeros for those smaller than 100. This is important for the proper page order when creating a pdf. If you have more than 999 pages, just increase the number of digits.
6. create a PDF out of the resulting files
Investigate the created page_xxx.JPG files, and fix the order if needed. For example, if you took a snapshot of the cover, rename the page_000.JPG to page_xyz.JPG, where xyz is a number larger than the number in the filename of the last page.
convert page_*.JPG book.pdf
7. clean up
Check the result and remove any unwanted files (like original images and “page” image files).