Has anyone here written and published an IT book? Please, share your experience.

I have an idea for a book, and I am willing to sacrifice some time off work to write it. For this, I will need to find a way to cover some of the costs of writing the book, while doing it.

I am interested to know how this experience might have been for others. How did you measure people's interest to invest in your idea? Is it reasonable to try and set up a crowdfunding campaign up-front, or going straight to a publisher is better?

Any tips you might offer would be more than welcome.