It's elementary...when you're with world-famous detective Sherlock Holmes and his trusty assistant Dr. Watson, you're sure to find fiendish felons, uncover nefarious plots, and meet up with the wicked Moriarty. But, in order to crack these cases and reveal whodunit, you have to sharpen your wits by breaking secret codes, unraveling anagrams, solving logic puzzles, and figuring out tricky brainteasers! Put your powers of deduction to work--and prove you're smart enough to outwit the cleverest criminals!
The logic puzzles in particular brought me back to doing those in Gateways in elementary school. They are very fun. There are lots of math puzzles in here too, and I'm definitely not as good at those. The Sherlock angle is totally just a framing device and the puzzles could have been about anything. After a while it gets pretty repetitive. I enjoyed it, though.
Edited to add: the majority of the answers do not have any explanation, so if you don't "get it" on your own, this probably isn't going to help you.