[teddyuk]

I've just signed a contract to write a book and I get an advance and then 10% (goes up to 12/15% if more are sold).

One major reason is that I am more likely to finish it and get it done than if I rely on it myself.

Another reason is that I want to be known for one niche, this will help and if that works out then I could likely self-publish and keep more of the profit.

It is slightly more nuanced than I want as much cash as possible for this thing.

[ghaff]

Publisher deadlines are both a blessing and a curse. I did the last book I wrote through a publisher. It was a concept I'd had bouncing around in my head for a while but hadn't made much progress on beyond a rough mental headline. When a publisher wanted to run with it, it forced me to focus on it--fortunately during a period when doing so wasn't too onerous.

On the other hand, I've had other periods when it would have been difficult.

The other thing with publishers is that you're now tied into publishing industry economics. So you can't typically write, say, 100 page book even if that's what you think is the best match for you and the subject. (This is probably the thing that would be most likely to keep me from using a publisher the next time.)

[pc86]

Does the 10% go against your advance or does it start immediately?

[dhosek]

An advance is, just what it sounds, an advance payment on royalties. Publishing, unlike film/tv or music generally doesn't play games with royalties, so, if the book sells, once you've earned enough royalties to cover the advance you will get additional earnings.