^ Bloodlines is the first book in Richelle Mead's spin off series of Vampire Academy. It is set to be released on the 23rd of August in English speaking countries. The book will be on Sydney Sage's POV, the alchemist in the VA series. Since you mentioned you're already reading Blood Promise, I'm quite sure you already read about her
. The second book in Bloodline Series was also already mentioned by RM "The Golden Lily" which will be release sometime in May 2012. Hope it answer you question.
Here's the 1st chapter
of Bloodlines in case you want to read. But I would suggest that you finish reading VA series before reading the 1st chapter of Bloodlines. There's some spoiler in there.