Aldarc said:
So do you buy two chapters of a novel just so you can buy the book again with the same chapters included?
And to be fair, this preview book is a giant advertisement for what will be released five months later.
You're spot on target. It's a poorly thought out attempt at generating revenue during the dead zone between now and 4e. WotC is betting it all (well, not ALL, see below) on the MMORPG marketing horse: "Hey, people will buy a guide for World of Warcraft, I bet they'll buy a preview of fourth edition... and then pay ten bucks a month!"
"If you don't like it, then don't buy it." WotC has fired you as a customer.
But it isn't all bad.
Grand History of the Realms? That was a great book to fill the edition gap. It's really too bad we couldn't have more system-less capstone products, like a Grand History of Greyhawk.
Dungeon Tiles? Another good idea for products during this period.
The Dungeon Survival Guide had the potential to be a good product... well, it was a great idea, at least. Be sure to pick it up at your local used bookstore.
The Rules Compendium? Good idea, mediocre execution... but then again WotC doesn't want to give us too many reasons to stick with 3.5, so might as well leave it a mess like they did with 2e.
The Part-Time Sorceress Book was another brilliant and innovative idea. Too closely tied to 3.5 mechanics (why not make this a 4e preview as well) and I was a little dubious that it didn't have any review blurbs of female authors. In any case, it flew off the shelf at my FLGS.