My personal FAVOURITE of his four novels!! Now I'm on to the short stories :)
adventurous dark mysterious slow-paced
Plot or Character Driven: A mix
Strong character development: N/A
Loveable characters: Complicated
Diverse cast of characters: No
Flaws of characters a main focus: Yes
adventurous mysterious medium-paced

Thrilling mystery in the first half, unnecessary (but intriguing) backstory in the second half.

My full review of this book: https://daariga.wordpress.com/2015/05/24/the-valley-of-fear/

Harold, they're Freemasons!

Best of the novels by far, if only because ACD totally dumps Holmes and goes off on a lovely Western mob-infiltration thriller tangent for 60% of the book.
adventurous dark mysterious medium-paced
Plot or Character Driven: Plot
Strong character development: No
Loveable characters: Complicated
Diverse cast of characters: No
Flaws of characters a main focus: No
adventurous challenging dark mysterious fast-paced
Plot or Character Driven: N/A
Strong character development: No
Loveable characters: Yes
Diverse cast of characters: Yes
Flaws of characters a main focus: No

El valle del terror no es, desde luego, de mis libros favoritos de Sherlock Holmes. Menos mal que Recuerdos es mucho mejor.
adventurous mysterious tense medium-paced
Plot or Character Driven: Plot
Strong character development: Yes
Loveable characters: Yes
Diverse cast of characters: Yes
Flaws of characters a main focus: Yes