I've been a professional technology writer and editor for 15 years. Most of those years were spent as a full-time freelancer, and yes, I made the stated financial goals for most of those years, usually at the high end. Yet, with all these enthusiastic book reviews and people claiming how much they learned from The Well-Fed Writer, I thought it was worth my time to find out why this book is so highly regarded. My conclusion is that it has good information, but it also has a few faults which mar its value.
Let's address the good stuff, first. Bowerman does a good job of encouraging the timid wage slave into the land of working for oneself. If you've been wanting someone to talk you into this career, this book will undoubtedly do so. He also gives a pretty good overview of the different kinds of writing with which he's personally acquainted, which means writing marketing copy. Most readers will walk away with a reasonable sense of how the business side of writing works, and that's a good thing. He has a bright and encouraging writing style, so this is not a painful book to read.
However, I've been editor at several technology publications (as well as writing thousands of articles, a handful of books, product manuals, white papers, newsletters, and more). This has put me in front of a lot of writers who truly want to make a living as freelancers but -- despite the pumped-up "you can do it!" Right Attitude that Bowerman encourages -- simply aren't going to make it.
The biggest reason is that *wanting* to write well doesn't mean you *do* write well. He glosses over the section on "have someone you trust evaluate your work," and I wish he gave more advice here. As just one fer-instance, *don't* ask "am I good enough?" advice from someone who cares about you and knows you well; they'll be positively disposed towards you, and an editor won't. Also, someone who knows you well will "hear" your voice in the words written down, even if it isn't there.
Plus, he assumes that any good writer can write well in any genre. It isn't true. I've worked with book authors who can't write an article, and vice versa. I've seen people who can write a how-to but can't write a product review. Personally, I find it so difficult and slow to write decent marketing copy that I soon realized that I couldn't make money at it (and I hated trying, even though "the money is so much better!").
Succeeding as a freelancer requires several attributes. Yes, you do need to know how to write well. You also need to know how to write for your audience, which is a skill that many lack (I know, as I'm the one who rejects their manuscripts). You also have to do so on deadline. And you have to be able to write well _fast_, to market yourself relentlessly (finding the balance between "persistent" and "pest"), and to remember to send invoices (a surprising weakness but one I encounter regularly).
Because Bowerman comes from a sales and marketing background, some of these skills come more naturally to him. Maybe they do to you, too, but I know how difficult it was for me to learn to drum up business. It took me a few years to learn and adjust to my own weak spots both as a writer and businessperson.
One thing that wasn't a problem for me (or apparently Bowerman) but is very real to others is learning to motivate oneself as a home-worker (which most freelancers are). He covers this last point, but since he's busy telling you that you'll succeed, you may not be aware that maybe you won't.
That sales background occasionally irritated me, because he's so busy reassuring you that you _can_ do this that he leaves out sections on "when to know if you've failed." (Mark Twain said, "Write without pay until somebody offers pay. If nobody offers within three years, the candidate may look upon this circumstance with the most implicit confidence as the sign that sawing wood is what he was intended for.") And I sure wish he warned readers that there will inevitably be a day where you're owed $20,000 from clients who are good for the money, but you don't have the cash to pay your bills today.
Whew. All that sounds as though I'm trying to talk you out of reading this book. I don't mean to do so; it's a good book. It's just not the only book you should read before you quit your day job and embark on this new career.