I always am suspicious of Holmes-Pastiches that were written by non-British authors and I don't even know why. It's a rather silly attitude (and the last German Holmes-pastiche I read was only mediocre but that certainly was for reasons that hadn't anything to do with her non-Britishness).
This book definitely already gets a million stars for not pulling that 'Look we found this manuscript on the attic/Watson did not want to have this published until 100 years after his death'-crap. I hate it. We all know that Holmes wasn't real so there's no need to pretend he was and make up elaborate stories why this story hasn't been published earlier.
The author also seems to have quite an attention for detail. I first was somewhat confused because Watson's turn of phrase seemed really odd but then I realized that it makes perfect sense: He's an Englishman who learned German as a young student (because reasons...well it sort of makes sense in context) but didn't really have the opportunity to speak it in his later years so now he has an English Gramar in German sentences which is quite a brilliant idea from the author. On the negative side I can imagine that becoming annoying if he keeps that up for the whole book so let's hope Watson quickly remembers German Grammar after some time in Vienna.
Overall just 15 pages sample weren't really enough to get a proper impression of the book. Watson arrived in Austria, met his old school-friends and that's it.
Then there's also the minor issue that in the book Rudolph's death is made out to be murder and some big conspiracy (well I don't know that for sure but it's unlikely that the author decided to write a whole book where Holmes decides in the end that it was just a suicide...) and I don't really believe that Rudolph's death was a conspiracy...and the last time I enjoyed a fictional retelling claiming something was big conspiracy even though I didn't believe it was the From Hell-movie...and that was mainly because Johnny Depp is just really handsome...
Yeah...I just used many words to say that even after reading the sample I'm still not sure if I want to read the whole book.