Won't lie, I first thought the image said "Defend the Book"

It's countdown clock is wrong.
https://www.gog.com/promo/20211026_launch_promo_defend_the_rook

All I see is a giant Orko.

Your forgot to add the world "purple". But yes, I do also see a giant purple Orko from MotU.

So, can someone comment, how is the game? The description on the game's page says it is a kind of rougelike tower defense with additional things...

"Defend the Rock" in my case.

I thought it said "Defend the Room"

It looks very much inspired by Into the Breach, but with fancier graphic and a 9x9 board instead of 8x8. But it doesn't let you see see the enemies incoming moves, which were the very thing that made the strategy in Into the Breach sparkle.

Edit: Besides also being an isometric chessboard roguelike, It looks like it's a quite different game after all.

When it said tower defense I was expecting on rail gameplay but I'm surprised with freedom of movement on somehow a limited space. But the demo is here I guess I can try it first.

I recall a game of the ancient past having a similar premise...
Found it: [url=https://en.wikipedia.org/wiki/The_Horde_(video_game)]https://en.wikipedia.org/wiki/The_Horde_(video_game)[/url] (c. 1994)

It's odd GoG doesn't have it.

Edit: Editor doesn't like URLs with parenthesis.

Looks interesting.

https://www.gog.com/game/defend_the_rook_tactical_tower_defense_demo

Doesnt appear to show demo on the game page and had to go looking for it. Really GOG..

Did they literally name this as such because "Defend the Tower" was slightly too on the nose?

Oh, there is even a demo, thanks for the link!
And bad GOG, bad... why don't you include a link on the game page? :(