The world-building was good and somehow the combination of historical characters, fictional characters from other works, steampunk, supernatural, time travel, parallel dimension, alternate history and secret cults didn't come off as overkill.
The main characters were likable, the three guys were all swoon-worthy and regarding the love triangle I would have been happy with whoever she ended up with.
I liked the development of the friendship and would like to see more of it in the next books.
The ending was disappointing, and I hope that the huge question that wasn't answered will be addressed in the next books. One of the core points of reading a mystery is finding out who did it, and I didn't feel satisfied by the answer I got.
Other than that, my only complaint is that Dylan, the guy from 2016 sometimes talked like the rest of the characters, who are from the 19th century.
Overall, the book was extremely entertaining. I don't read many steampunks, so the concept felt new and original, even though it might not come off that way to a reader more accustomed to the genre,
But it also was terribly forgettable. I'm writing this review less than 48 hours after I finished the book and I already forgot most of the characters' names. Really. I had to look up Dylan's name and I can't remember what Bram Stoker's sister was called. And she was one of the main characters.
If you're looking for something quick and fun and entertaining, read it.