My suggestion is not to send the disks out but to load all the data onto a web site - its cheaper and you can protect it with passwords for a start.
You can also load up lower resolution images with watermarks that are unsaleable on ebay etc.
The web site will be easier to maintain as new data is obtained and you can build a forum facility to allow members to pass requests and info between themselves.
You will save the distribution costa and have a far better chance of stopping theft of images while making the info accessible to legit members.
Heres a forum some friends started recently. (the software is not expensive.)
www.openpitlane.co.uk
Thats my starter for 10 as we say here.
Now about the book.....