It's out tomorrow, and this is the cheapest price I've seen for the PC version. It's important to note that this expansion also comes with the base game, making it an ideal version to get if you've yet to play ESO.
As the title gives away, Morrowind takes place in the fan-favourite region of Vvardenfell in which players try to save Vivec City from destruction. The way content scales to your level also means newcomers can just dive straight into the expansion alongside experienced players, or go through the old content first. This pre-order also comes with the Discovery Pack that includes a bunch of extra goodies as well.
In short, there's a lot of game there for £23.99 if you're after a subscription-free MMORPG to play.