In the latest tale of the Vampires, Louis is consumed by an obsession to call the spirit of Claudia, so David seeks out a member of the Talamasca who might be capable of doing so. Even though we have not heard of her before, David shares a long history with Merrick, which he relates to us here. They even go on a trek through the South American Rainforest!
This book seems more like a bridge between two tales than a story that can stand alone. One must be completely familiar with the characters and their history to really appreciate this adventure. It was worth reading, I think, if one intends to continue to read the chronicles, but not for its own merit. Ultimately, my opinion is "meh."