Electronic Discovery for Dummies review

I just finished the free Electronic Discovery for Dummies booklet that Mike McBride blogged about. It didn't take long to read as it was 42 pages but it was quite interesting. Like Mike's review I found the book easy to read and a good start for IT Managers or someone who may need to talk to a CEO to explain implications of IT practises. In my case it will be useful to explain the implications of mail (and data) archiving policies. Several questions have arisen lately about archiving and deleting mail to reduce the load on the mail servers. Some of the reasons for doing this is cost, but then recovering all the data from all of the backup tapes could prove far more costly. However, having a short retention time for backups seems to be acceptable as long as the company has a strict policy for this and that it is adhered to.
I'm not sure what happens or if it is possible to have different retention schemes for different users (or management levels) but I do know that whatever solution is used, the ability to stop deleting things according to the policy must be possible in the case of an ediscovery request.
I passed the book along to one of our sales people as it is a good, quick primer and should really be required minimum reading for any tech dealing with backups, restoration and deletion of software.