It's a good book. I've enjoyed it, and bought copies for co-workers. However I do find it a bit dated. Overall the guidelines are great but I wouldn't try to emulate the style. Also I wouldn't bother reading much of the information related to the application of copywriting to specific technological implementations.
I've had a number of businesses over the years, written a lot of business plans. This book is one of the best on business plans I've read. It's pretty comprehensive without being dry. I quite like that the author doesn't show you just what sections you need, but why, and how.