I think this is a good move. I loved the combo of the FRCG and Monsters of Faerun for the 3e Forgotten Realms (the only 2 books I bought for that line). I thought the Player/Campaign Guide strategy for 4e FR was a really bad choice. As The Little Raven points out, it makes even more sense to have a seperate monster book and a single campaign/player guide for DS.