....won't sell very well if it's sent to the wrong market and if you really have want your targets want, then a very ordinary sales letter will do the job.

The trusty old AIDA formula is the best way to write copy, there are many variants of it, but AIDA's all you need.

The best book I've ever seen about copy writing, direct mail and general product development is Bill Myer's '301 Direct Mail Tips, Techniques & Secrets'

It covers everything and it's snipet format is very user friendly.

Jeff