Congratulations for creating a great project! And of course, congratulations for an impressive achievement of writing a book!
The idea itself is something really new, very unique and opens vast range of possibilities. The concept of mix between past and future is something very unnatural to people's eyes and I think that's exactly what people unconsciously want.
It reminds me a bit of a movie called "The League of Extraordinary Gentlemen"
However, I won't lie - there is a lot room for improvement. At least from the images the level of detail in some maps seems too low for Source engine. Some places look great, but some look like it's GoldSrc. Also, I think it's quite repetitive in some places. The neon letters look very similar everywhere. Lighting too. The connectivity between old and modern could be a bit better. For example the modern glass building doesn't blend with the surroundings well. I could compare it to early HL2. You guys really need to polish everything a lot. But it's not a problem. You have a strong base - great story, big team, a book and the project itself seems very quality. This is definitely going to be a success, but you must not hurry! Also, I would really, honestly recommend to get rid of this yellow color correction/color tint or whatever it's called. I just think it makes things look boring and not alive.
The trailer is composed really great but production itself is pretty unprofessional. Some scenes seem like straight out of Garry's Mod.
So, I think it's just a matter of time. You should eventually go from a level similar of early HL2 to HL2 as it looks right now. Your game looks way better than early HL2, I must say.
Sorry for quite a nasty amount of negative feedback but I just want it to turn out even better! Good luck, my friend!