MS Gundam UC 1 The Day of the Unicorn (First)
* 機動戦士ガンダムUC(1)ユニコーンの日(上)
* Release date: February 1st, 540 Yen (inclusive of tax).
* Cover image to be done by Haruhiko Mikimoto (美樹本晴彦), other illustration done by Kozo Omori (大森倖三).
MS Gundam UC 2 The Day of the Unicorn (Last)
* 機動戦士ガンダムUC(2)ユニコーンの日(下)
* Release date: February 1st, 540 Yen (inclusive of tax).
* Cover image to be done by Haruhiko Mikimoto, other illustration done by Kozo Omori.
The Day of the Unicorn (First) MS Gundam UC 1
* ユニコーンの日(上)機動戦士ガンダムUC(1)
* Release date: January 23rd, 500 Yen (inclusive of tax).
The Day of the Unicorn (Last) MS Gundam UC 2
* ユニコーンの日(下)機動戦士ガンダムUC(2)
* Release date: January 23rd, 500 Yen (inclusive of tax).
All 4 books are written by Hukui Harutoshi (福井晴敏), which are new novels based on the anime I believe. Being so close in terms of titles and pricing, I think the content is the same as well, just the illustration part separate the two.
For your information, the very first novel of Gundam UC, of the same title as the first book listed above, was released 2 years back at 672 Yen (inclusive of tax).
Information and image is from Kadokawa Web.