Aspects of the culture in the book...

 This book, "Sherlock Holmes and The Hound of the Baskervilles", was written in the beginning of the 20th century (1900-1901). In this time a lot of things happened in England. 

Britain in those years has evolved some changes in politics and economics, and in culture. First cars start to go on roads of England in the early 20th century. In this book we can read that Sherlock use a carriage with a horse. But it's only the beginning. Also British started to use the first phones, gramophones, etc. 

 

As for the fashion of The Great Britain in the early 20th century. Formal suits was in fashion in this time. This suits included pants, vest, leather gloves, cane, hat. As for me I imagine that Sherlock Holmes wore this suit. Yes, I think so.

The 20th century was a period of the development in Britain. Some restraint prevailed in an architecture of London. A lot of houses was with two floors.

 Like that:

So, in this book, there are not a lot of aspects of the Britain's culture in early 20th, but this work is this aspect. Conan Doyle lived in this time and his works are a part of the Britain's history. If you want to learn about old London you must read all books by Sur Arthur Conan Doyle.