No, it's not a vampire. A blad is a dummy or partial book produced for publicity purposes ahead of publication. Blad = Book Layout And Design. Typically, it has the front and back cover and a sample of inside pages. It's most useful for illustrated non-fiction as it can give buyers (industry buyers, distributors, foreign rights dudes) a good idea of what the book will be like. It may be stapled or spiral bound. The blad can be produced before the book has been completely written, but then there is an obligation to deliver the whole book in the style and design used in the blads.
Blads are, I suspect, an irritation to editors. Although it focuses the mind on getting the design sorted, the blad can become a project in its own right and use time and resources that should be devoted to getting the book finished and produced. Maybe editors don't think like that - but as a writer, I've sometimes had to put the book on hold in order to work on the blad, which somehow appears unannounced in the schedule demanding immediate attention. On the other hand, an attractive blad makes me enthusiastic about finishing the book, so it has its uses even for the writer. Seeing the blad is a little trial run for the thrill of seeing the book, and a useful spur when the going gets tough, or just dreary.
Not all books get a blad, and not all publishers use the word 'blad' even if they produce one. I rarely see blads for my books these days, which might mean there aren't any or it might mean I just don't see them. If a book is one of a series, there's likely to a blad for one title and just AIs (advance information sheets) for the other titles. Oops, I don't think we had an 'A' entry for AIs. Will add one!
The best blads I've had were produced by Dorling Kindersley. They were so luscious I felt we didn't really need to bother with the book. (But we did.)