Years ago, I found an anthology (edited by Howard Hayes) in my library called "The Boy's Book of Detective Stories" or something similar. It introduced me to The Thinking Machine (by Jaques Futrelle) , Max Carrados (Ernest Bramah), The Old Man In The Corner (Baroness Orczy), Uncle Abner (Melville Davison Post), Dr. Thorndyke (R Austin Freeman), Martin Hewitt (Arthur Morrison), and a few others, all published before 1940.
This year, I've been visiting gutenberg.net & gutenberg.net.au and found them again. I've read quite a few more stories featuring each, and they are quite enjoyable. Casual racism does show up from time to time (I've noticed that in some of the early Ngaio Marsh mysteries, too), which takes me out of the story. Some are better than others - SS Van Dine, author of the Philo Vance mysteries, has surprised me more than once by undercutting at least some of the racism expressed by some characters by the words/actions of other characters.
By the way - if you're interested in forensics, definitely check out Dr. Thorndyke.
(edited to remove a surplus sentence.)