A long time ago someone recommended to me a small Norwegian book called Sophies World [0] as a very basic introduction to the history of philosophy and its served well.
It was written by a teacher and geared at young adults. So its not a rigorous introduction. But its a short read and by the end you'll have enough leads to follow.
I'd also recommend Sophie's World as a jumping off point into multiple "canon" works as referend by another poster.
I'm sure people out there criticize it as not rigorous or full of inaccuracies, but I've found it an easy read that gives a good overview into the works of western philosophy.
I’ve seen many syllabi that include this book. I haven’t read it myself but have met some smart/thoughtful students of philosophy who did and value it highly.
This is actually what I came here to say! It is great book that I have given to many people. I also recommend Anathem, by Neal Stephenson which is a romp of a novel shot through with philosophy.
It was written by a teacher and geared at young adults. So its not a rigorous introduction. But its a short read and by the end you'll have enough leads to follow.
[0] https://en.wikipedia.org/wiki/Sophie%27s_World