This is a 2 book set inside of a plastic slip cover:
The Elements of Phantasy Star Universe: This book has art for both PSU and PSU: Illuminus. A very nice artbook, though it doesn't have art of the Landeel or the Military ships.
Phantasy Star Online - Ep III - Blue Burst - Visual Book: Not a lot of lineart / production sketches, mostly this is 'fan' art (though done by pro artists), some comics and a little bit of new stuff.