Does self-publishing work?
What is your goal?
My first thought is you are not asking the right question. I think it is necessary to ask what you want or expect from a book.
If the question is can you become a well know, best selling author by self-publishing, then I would say that very few actually realize that goal. However, that is not necessarily a limitation of self-publishing. The truth is that most books are not financial successes.
If you are planning to publish a book, it is very helpful to do some research on the publishing business. Are you planning to do a fiction or non-fiction book? Realize that it is much more difficult to be successful with a fiction book than a non-fiction book.
Another question you must answer is what is your goal. It is much easier to make money because you are a published author than it is to make money from the book. Bob Proctor wrote the book, You Were Born Rich. He said he has sold a few thousand books and have given away many thousand books. The books he sold did not do much for him. But the books he gave away made him rich. He did not make money off the book, he made money because of the book.
If your goal is to self-publish and retire young, don't quit your day job. On the other hand, if you want to use the book as a basis for establishing your status as an expert and selling some higher priced services, that goal is realistic and obtainable by most people who go about it the correct way.
Most people do not understand that the marketing of a book is much more important than the words in the book. A very high high percentage of books that are sold are never read. Large publishing houses are very poor at marketing. And for new authors the marketing by the big publishers is almost non-existant. If you do not have a platform, it will be very difficult to be successful with a big house or as a self-publisher.
The first thing you must do is determine if there is genuine interest in your subject. You can check search engine results to see how many people are searching for information on that subject. You can also check to see how many magizines are published covering that subject. If the search engine traffic is low and there are no magazines on the subject, there probably is very limited interest in the subject. That does not mean that it might not be a profitable niche, it is just very narrow and will be more difficult.
If you establish there is a market and your intention is to use the book as a part of your marketing platform, then self-publishing can be the way to go. Realize that the economics of self-publishing is much better than the traditional route, once you recover your initial capital cost.
There is a difference between self-publishing and print on demand. If you just want to impress your friends, print on demand is great for a very limited number of copies. However you will never make any money with POD. And often times you give up the rights.
There is way too much information to cover in a short article. If you want an in depth, well researched book written by someone who has gone through the process and is making good money from it, I suggest you invest $15 in The Well Fed Self-Publisher by Peter Bowerman. (You can go to Amazon.com and read my review of the book for much more information) In fact, if you don't get this book or one that covers the subject before you start writing, you'll be wasting a lot of time and energy. Bowerman gives you a step by step process. He makes a great case for self-publishing. The book is a wealth of information, with details about cover designers, printers and everything else you need to know.