1) The author's stilted writing style. Mathews' choice of words seems entirely at odds with the story he is trying to tell, and serves only to annoy the reader.
2) Poor use of Vienna as the novel's setting. The description of the city often consists of little more than place-name-dropping (This, incidentally, is often marred by typographical errors, especially in the second half of the book, when it seems as if the editors have also lost interest. Actually, this is too bad, since Mathews' writing definitely improves as the Vienna Blood goes on). To this he adds rehashes of old quotations about the Viennese mentality. It is hard to shake the impression that the author does not know the city as intimately as he would like to have the reader believe.
3) The lack of a credible futuristic atmosphere. Certainly, there are all sorts of techno-gadgets and glimpses of life in 2026-27, but nearly all of the cultural references made by Vienna Blood's characters are to people, places and events of the 20th century. These characters, therefore, come across as likely inhabitants of the present day, not the 2020s, destroying whatever suspension of disbelief has been built up.
Unfortunately, these shortcomings are rather major, making it impossible to recommend Vienna Blood. While not a complete disaster, there are far better and more satisfying ways to spend an evening.
I found the language irritatingly florid-- Mathews seemed to be writing from some obscure rule that required using the most obscure word possible for any given possibility. And I can't imagine that I was the only person who found the ending quite distasteful-- what exactly was he trying to say?
Some nice Vienna atmosphere, but unless you're really bored, I'd skip this one.