Scanning is actually very quick and easy if you build your own rig. Take a look at
http://www.diybookscanner.org
If you really want to do it, this is probably the fastest way. For a ~400 page book, it takes me about an hour to scan and import the book, then another couple of hours to proof read the book. Depending on the book and how accurately you want to preserve it, it may take longer to proof. Things like typeface, font weight, indentation all take a little longer to make sure of.
- Ed