As Becca mentioned, I found the removed and formal tone of DWC to contribute greatly to the mood and message of the book. The book contains practically no dialouge and is nararrated in the past tense, creating an almost "documentaryish" feel to the book. In addition,Larson frequently employs phrases such as "a later report by a Chicago building inspector noted", referencing later additions to what??? This style makes the story sound like an investigation, as if the nararrator is searching for more clues and some answers pop up along the way. Larson also includes quotes from witnessesque characters such as, "a bricklayer George Bowman said", also emphasizing this detective like tone.
Adding to the suspense,sentences such as, "he first worked for Holmes as a common laborer, but soon proved to possess a talent which Holmes found particularly vulnerable", leave the reader on a cliffhanger, eluding to some seemingly important element of the story, but not disclosing the full story until much later. Personally, this has made the book much more enticing to read for me. I wonder if this will continue as the plot developes...