There are two kinds of 'writing software'. One is supposed to generate plots and all but write your book for you, which is the silliest idea since battery powered trouser zippers.
The other kind of writing software is just a word processor in slightly different clothing. Instead of keeping your novel in one long file (or a load of chapter files) this kind of writing software organises the books into chapters and scenes. That's all yWriter does.
I'm a programmer, and nobody sits down to write a 50,000 line program in a single text window. You'd be laughed off the planet if you tried, since it would be impossible to find anything quickly. Instead, we work with short code modules, which are held in source files. They show up in a tree view, and you edit a particular module by double-clicking it. The parts make up the whole. It's just so much easier to work on smaller pieces, while still being able to view the whole.
All I did was transfer this method of working to the act of writing a book. Several years back I was getting more and more confused the longer my book got, until I hit the wall at around 25,000 words. I could no longer check previous sections quickly, and splitting the book into chapter files meant I had nineteen copies of Word running simultanously.
A novel consists of chapters and scenes, and if you put the chapters into a tree and break them down further into scenes, you've got a structure the brain can work with. In yWriter you can drag and drop scenes between chapters, move chapters around, and open any scene in any chapter in its own editor window - simultanously.
I've written three novels using yWriter, and when time came to rewrite them for my publisher it saved me weeks of headaches. I used the scene description feature to keep notes about what needed to change, and used the auto-synopsis feature to print off a working framework for the book. AND I used the work schedule to see what I had to do every day to meet my deadline.
I put the software on my website for others to use, but I really don't care whether they write books with it or not. I'm not selling it, I'm giving it away, and I get nothing out of that than even more emails.
Still, it's very rewarding when someone sends me a message to say they're finally getting their novel into shape, thanks to my software. Every one of those makes me smile.
Simon Haynes is the author of the Hal Spacejock and Hal Junior series (Amazon / Smashwords / other formats)