It was written a few years ago, so it doesn't have the latest techniques for maximizing conversions for SaaS products.
However, it's written for direct response advertisers and not brand advertisers, so it covers the basics of getting sales, tracking, split testing, etc very well.
You can take the techniques Hopkins presents for writing short, effective classified ads and apply them very effectively, with minimal modification, to your AdWords ads and landing pages.
These techniques have been tested by dozens of advertisers since, and they work VERY well.
A good copywriter will usually charge $10-$15K plus a percentage of sales. I would strongly recommend bringing your copy skills to "Good enough" and doing it yourself.