If it is something as simple as a novel you can actually use a word processing program. (I know of people who produce relatively complex magazines using Word. My wife has written several books using Word.) Open Office and Libra Office are both free and will produce pdfs if you want someone else to print it. You need to check the layout on the pdf that is produced, but otherwise it is pretty straight forward.
Desktop publishing programs can produce better results if you are prepared to take the time to learn them. I have used Serif's PagePlus to produce several editions of a community magazine as well as tri-fold leaflets, birthday cards and screen presentations. You can download the starter version for free. I am not sure what restrictions it has, other than being an earlier version of the program. Normally, you are then offered an upgrade to the full program for a minimal price with no restrictions (I paid £10).
In the 1990's high end programs (such as PageMaker) offered features that were deemed necessary. Now-a-days cheap or free programs will do just about everything you could ever want. Unless you have very complex needs, I wouldn't pay for a premium product.
Personally, I never use Microsoft Publisher for three reasons. Firstly, it is very restrictive and doesn't allow you to do many things I want to do. Secondly, it is expensive. Thirdly, and this is perhaps the most important point, any document produced using the program is immediately identifiable as being produced using Publisher.