TITLE: Mathematical literature to lose yourself in
QUESTION [41 upvotes]: H.M. Edwards in the preface to his book on the Riemann Zeta Function, summarises his philosophy on learning Mathematics:

...I have tried to say to students of mathematics that they should read the classics and beware of secondary sources

In trying to learn more, I feel that I have accumulated a bookshelf full of secondary sources which I have left largely unread. So I would like to take heed of Edwards's advice and read some classics for the wonderment of it and for the respect I would gain for mathematicians of the past. I would like to exercise creativity over rigour, at least for a little while.
But this begs the question: what are the classics? And this is what I hoped to ask about.
Which primary sources do you feel are suitable for self-study? Naturally this is a broad question, but people must have their favourites, and I am hoping for some recommendations on the basis of these personal preferences.

REPLY [2 votes]: I should say that as far as recreational maths is concerned and you have tagged this question as such, going through this book will be a very satisfying experience: Winning Ways for Your Mathematical Plays (all volumes). Games were not taken seriously by mathematicians as you will recall Euler himself dismissing the graph theory field as not serious maths even after having solved Seven Bridges of Königsberg. This book tries to go that extra mile.