Can You Solve My Problems?

Don't worry, nothing is wrong. This is just the title of the book which I have been reading all week. 

Alex Bellos has put together a collection of maths puzzles which I have found challenging, amusing, and some quite baffling. But all have been a fun diversion. In one chapter he describes how the satisfaction he gets from completing a Sudoku grid is akin to that enjoyed by others filling in their colouring book. If you can relate to that, then I think you'd enjoy this book too.
Some puzzles require logic, others need calculation skills, or algebra or understanding of simple geometry. Many require you to spot the pattern [or the difference] I admit this is a very geeky, niche interest. But I am loving working through the challenges.
If you are wondering about the puzzle on the front cover, the answer is this;
It is the first square - simply because every other shape has reason to be the odd one out, but this one doesn't! [#2 has no border, #3 is round, #4 is blue, #5 is too small] 
If this means nothing to you, that's fine. But you may want to consider it for a Christmas gift for the maths nerd in the family.