Before the stars in your eyes and visions of accepting the Pulitzer Prize block out any view of reality, I need to show you the dark side of the mirror. First of all, you’re going to be alone when you’re writing. This is not the same as working at a regular job, nor even like contract technical writing. Even if you’re working offsite for a contract, you’re in contact with people. But your acquisitions editor is not like your project lead. You may not talk to your acquisitions editor even once a week. You will possibly talk to the project editor once a week and even once a day as the book is getting close to done, but the project editor is only interested in page count, style, and editorial and mechanical questions, rather than process and production questions.
You have no idea of what “alone” means until you’re 2/3 the way through a hard book contract and you’re running a month late. It’s just you in your office, staring at the monitor, and (hopefully) writing brilliant prose. You may be a writer that likes a TV or stereo on in the background, but it’s still going to be just you and the computer. The bottom line is that you just won’t have much contact with people while you’re writing a book except when you’re not writing.
As a result, you can get depressed easily, particularly if you’re having trouble with a chapter that’s just not gelling. You can also procrastinate easily. Before you start a project, you should be completely honest with yourself about what kind of procrastinator you are. You can get derailed easily. Set goals for writing productivity and be absolutely honest with yourself. (You don’t need to show this to anyone else with the possible exception of your therapist but you need to track your progress.)
One publisher I know says that as many as 75% of all computer books are delivered from one to six months late. The reasons for this are many and varied, but most commonly, it’s because the authors lose focus, they get overbooked (one project runs late and slides into another), they get depressed, their support system breaks down (or their significant other loses patience with the enforced solitude), or because they discover they just can’t do this one.