Read Poe first then Doyle.
This is a pdf file of an entire book which may be useful to you if you
write about Poe's Dupin stories. Be careful because the page numbers you
see in the corners do not match the ones on the actual pdf file. In
other words, if you print up pages 25-35, you're actually printing up
pages 15 to 25, so just go to the first page you want to print, move the
mouse to the bottom of the screen where a menu should appear, start
printing from the page number on THAT menu, not the page number you see
on the actual page.
Read only the Murders in the Rue Morgue for Poe.
Edgar Allan Poe Dupin
Murders in the Rue Morgue
The Purloined Letter
The Mystery of Marie Roget
Arthur Conan Doyle "A Study in Scarlet"
Just the first two chapters of the Doyle novel. They're numbered 1.1 and 1.2, so just read those.
The main item to consider is the evolution of this type of character from Poe to Doyle.