This is a bit late, but perhaps will help others: I came across an invoice from the mystery vendor "Vendome Group" www.vendomegrp.com . They appear to have purchased all the real estate and leasing titles from Brownstone's back in August 2004. I found this brief note about it.
Education products appear to still be published by Brownstone's as a subsidiary of Vendome.
HCPro purchased Brownstone's health titles in October according to this notice.
Good of them to tell their customers! Vendome and Brownstone's can be contacted at 1-800-519-3692. Remnants of Brownstone websites still exist on the web if you google their name.