For almost a year now, Toranoana has been having gallery exhibitions of popular artists, and at these events you can buy a large B4-sized 'pamphlet' that includes the artists' works that were on display in a book format. Alpha's (有葉) gallery was the most recent one, having ran from May 19th through the 28th and the amusingly titled Pictures at an Exhibition of Alpha was the companion pamphlet.
AKABEi SOFT2 Illustration Collection is an art book much in the same vein as previous memorial illustration books to have come out over the past year like MOONSTONE Complete and Circus 10th Visual Album. The major difference with this one is that AKABEi SOFT2 hasn't really been around anywhere near long enough to bring out this kind of memorial collection. I think they just jumped onto the recent trend with this one ^^;