"<Some file> not found." Error
Try running through the installation steps again as shown above.
"./library/book/images... Permission denied" Error when running Decapod 0.6 server
You may need to change the permissions on the decapod-server/book directory. Alternatively, you can try running Decapod using sudo python ./decapod.py
If you start the server using sudo, you will always have to run it with sudo, as the permissions of the created directories will be restricted by it.