So, I just checked her official site, there's nothing about the BEST album.
But I checked fan-net, and they have it titled as :
Mai Kuraki BEST "MERRY MUSIC!"
I hope her artist name isn't really in the BEST album title. It just looks a bit strange I guess.
The release date is still July 1st, so I hope we will get some updates soon. *ahem CDJapan & her official site*.
Oh, and fan-net's description of the album is 10th anniversary BEST album.
Plus also, the "Beautiful" single has this sticker and label that mentions it is her 10th anniversary, so I guess her record company are really promoting that fact a lot.