The back cover of this collection says the stories "easily match or beat Arthur Conan Doyle's master detective," which aside from not really making sense is just blurbtalk. With a few exceptions, these stories are deservedly forgotten and lacking style, character, interesting plots, or any sense of how to structure a mystery.
Those exceptions include a Sherlock-less train mystery from Sir ACD himself, who shows up like Springsteen at SXSW to show the kids how its done, and the funny and ingenious "The Problem of Cell 13" by Jacques Futrelle, featuring his fantastic Thinking Machine. And at the other end of the spectrum is "The Stone of the Edmundsbury Monks" by M.P. Shiel, one of the most enjoyably terrible mysteries ever written, which I wrote more about here.
The book itself is an amateurish production, with one of the least appealing covers I've ever seen and art-school-quality illustrations that are unattractive in the most boring way possible. Rookie mistakes abound, including footnotes appearing on the wrong pages and the lack of any information about the man who edited this collection and wrote its notes and introduction, Leslie S. Klinger. That's a slap in the face to Klinger, who's one of the world's foremost Sherlockians (not to mention the editor of Neil Gaiman's new The Annotated Sandman.)
Anyone without a truly compelling interest in Victorian detective fiction can pass this up, or better yet put the $16.99 towards Klinger's perfect The New Annotated Sherlock Holmes.