One of the problems with publishing technical books is that editors must decide, in advance, whether or not they feel a given topic will be popular enough to merit publishing. The sales must outweigh the costs, hopefully by a wide margin.
Mind you, this has been mitigated somewhat by publishing in PDF format and minibooks (as the Pragmatic Programmers have done), but you're still guessing, even with those formats.
Cue the game publishing industry. There's a company called GMT Games. Because the margins are so low on wargames, and because you can never predict in advance whether or not a game will be popular, they came up with a new concept called the "Project 500" (aka the "GMT 500"). You can find the link at the top of that ugly 90's style web page, btw.
Quite simply it means that they wait for at least 500 pre-orders before actually publishing a game. In the meantime, they provide you with a description of what the game is about, the style of game, the author(s) and perhaps a few screenshots. Once they hit 500 orders, the process of moving it into production begins and, if you've pre-ordered the game, you should see your copy in the mail in about 6 months. Oh, and you aren't charged until the game actually ships.
Mind you, authors might not be too thrilled with the idea of working on a book that might never be published, but then that hasn't stopped the game designers.