Some classic logic and probability puzzles are dressed up as Sherlock Holmes stories, with the mistaken reasoning of the victim (and Watson) clearly pointed out, and the right reasoning lucidly explained. The author's aim is to make the tales memorable enough that they should be applicable in real life. To that end, he often has the same puzzle occuring twice in different guises, once to the victim, then again to the hapless Watson. This works very well.
The vignettes are enlivened by amusing speculations about what will happen during the Twentieth Century. (My only nitpick is that 1900 was not the start of the Twentieth Century, any more than 2000 was the start of the Twenty First, and moreover, the inhabitants of the time knew that.) All in all, a fun read, with stories that should stick in the mind ready for that fateful moment when they become relevant.