Well, this is something you could write a book or two about, and in fact, they have been written! But let's take this as a serious question, since I've spent a fair amount of time in the last decade or so writing computer books myself.

First off: don't go into writing a technical book with the expectation that you'll make any money. You also don't want to keep track of how many hours it takes to write a book compared to your payout, advance or otherwise. It'll just depress you. Of course, this doesn't mean that you can't do well with a solid tech title, but unlike the heyday of the late 1990's, a technical book that sells 5,000 copies is considered a success in the industry today and if you do the math, that's not going to buy you a house in St. Thomas, or even a shiny new Harley.

So why write a technical book? One good reason is because it's a great calling card, a demonstration that you're a thought leader in your field and an expert on the subject. There's a certain cachet about being a published author too, one that I've always found a bit puzzling: people think it's quite literally amazing to find that I have books on the shelf at the local bookstore and that I'm even in the library database. This translates to the professional world too, and it's a rare hiring manager who can resist the urge to favor an applicant who has "written the book" on a technical subject.

Another reason to write technical books is that it's fun, believe it or not. The process of taking a large and complex topic and present it in a way that makes it understandable and interesting to a wide range of readers is a delightful intellectual challenge and it's quite rewarding to hear positive feedback from readers and receive good reviews on Amazon and in industry publications.

Before you leap onto your word processor, however, it's worth spending a little bit of time talking about the ins and outs of the publishing industry...

A first-time author is likely to see royalties of about 8-12% on sales, hopefully staggered based on hitting specific sales milestones. For example, you might be paid 8% of the first 3000 copies, 10% of the next 2000 and 12% thereafter. More established authors typically see better royalty terms, but there's not a vast amount of padding in this particular publishing niche, so don't expect 25% or 30% royalties for even the most astonishingly wonderful title.

The other half of royalties is the advance, which you should look at as payment for the time you're going to spend writing the book. It's not magic, and it pays to be very thoughtful about any offer that trades a lower royalty against a higher advance. A first-time author will probably see a $5000-$7500 advance, spread across signing the contract, submission of the first third of the book, submission of the last chapter, and final edit of the last chapter just pre-publication.

How much you should seek as an advance is dependent on how well you believe your book will do: if you think it'll be a best-seller (and be realistic, it probably won't, alas), then push for a small advance but better royalty terms. If you're more cynical (or, I might say, realistic), then try to get the largest advance possible because it's quite possible that the book will never sell enough copies to earn out and begin to generate a royalty stream for you.

In my experience the following players are involved in a technical book project too: the acquisitions editor is the shill, negotiating your contract and getting you excited about the project. You sign the contract and, like a will o' the wisp, the AE pulls out of the picture and you're working with a development editor. DE's can vary all over the map, from being very hands-on and hacking on your manuscript to the point where you wonder if they shouldn't just be listed as co-author all the way to an occasional cryptic "latest submission good. next due?" I prefer someone that's in the middle of this continuum, paying attention to the project so that we can leverage the synergy of more than one person working on the book, but not so engaged that I lose my voice in the process or keep hitting a brick wall with long-overdue feedback.

Along with the development editor, there are copy editors who are the Grammar Police (usually painlessly, but sometimes they can be a nightmare, as when they correct the grammar in error messages or compiler flags) (and you think I'm kidding!), and at least one technical editor, who is responsible for vetting the content of your manuscript rather than the prose (I do a lot of tech editing).

As the book nears completion, one or more people from the marketing and public relations team will get involved, working with you on cover design, prose for the back of the book, and even the wording of press releases and catalog blurbs for promotional purposes. If you're with a good publisher and your book is of reasonably general interest, they can also book you on radio programs, arrange for signings at conferences, and similar.

That should give you a bit of a flavor of the technical book publishing industry. Still interested in writing a book? I hope so, because goodness knows there are a lot of terrible technical books published every year, books that are inaccurate, incoherent, or just plain don't explain their subjects very well. There's always space for a new author, just don't pre-order your new Rolls Royce, okay?