The cover has been tweeted, which can be seen here for those who don't like using twitter.

As Paulbot noted in the first posting, the publication is being called a "mook", which is said to be a book that is more like a magazine (I guess small enough to not have a spine), and to be made available in stores that sell magazines, but for longer than a magazine (which would usually be a monthly publication).
Since a number of sources (and the cover image) is saying that this thing is a "mook", it probably isn't as big as previous Generations books (no page count is noted anywhere that I can see)... and it pretty much looks like it doesn't include the annual collection of toy images like the Generations books (which sucks, as they make up a great collection).

Saying that, the price is more than what the Generations books have been priced at (usually about 3000yen), so... either it is bigger than the Generations books, or this new business just charges a lot more for their products.

The Amazon Japan listing - December 3rd - 4378yen (about AU$58-60).