If you go into my parent's bathroom, and there is no real reason you should, then you'll find a series of find-a-word
The basic premise is you have a large group of letters and hidden within them are certain words. The easy find-a-words just have letters up, down and diagonally, but when you get into the complex find-a-words the can be curved or at angles.
These are very difficult and I try to stay away from them. I have a hard enough time with the easy ones. What makes these kind of books special is most of the puzzles are themed. It could as general as plants to as specific as a certain film or television series.
They have them for all levels from small children to adult and the main differences are the types of words and the size of the puzzle boards. I grew up playing these games and they are great for mental fitness. I would first do a quick glance to see how many of the words I could find without really looking and then I would do a systematic find of each word.
You can pick them up and put them down at anytime. There is no time limit, which makes them a great way to kill some time. When its time to go, you just set it down and it will be ready for you when you return. Just watch out that someone else doesn't pick it up and finish what you started.