Bressoud, David. A Radical Approach to Real Analysis. Mathematical Association of America, Washington D.C. 1994.
A genetic development of the basic notions of convergence.
Courant, Richard and Fritz, John. Introduction to Calculus and Analysis I. Springer 1998.
A reissue of one of the classic calculus texts.
Steele, Michael. The Cauchy-Schwarz Master Class. Cambridge University Press, New York 2004.
An engaging introduction to inequalities.
Hoffman, Paul. The Man Who Loved Only Numbers. Hyerpion, New York 1998.
About Paul Erdos.
Nasar, Sylvia. Beautiful Mind. Simon and Schuster, New York 1998.
About John Nash.
Wilf, Herbert. Generating Functionology, 3rd ed.. Academic Press 1994.
Treats the application of power series to combinatorial problems. The second edition of the book in pdf format is available for free at: http://www.math.upenn.edu/~wilf/DownldGF.html.
Conway, J.H. and Guy, R.K.. Book of Numbers. Copernicus, 1996.
Discusses the many amazing properties of the integers and integer sequences. Graphics in this book is striking.
Apostol, T.M.. Introduction to Analytic Number Theory. Springer-Verlag 1976.
A comprehensive introduction to number theory aimed at advanced undergraduates and graduate students.
Oliver, David. The Shaggy Steed of Physics, 2nd ed.. Springer, 2004.
A poetic book that uses the classical two-body problem to motivate many of the fundamental ideas in modern physics.
Grimmett, G.R. and Stirzaker, D.R.. Probability and Random Processes. Oxford University Press, Oxford UK 2001.
Comprehensive introduction to probability good for upper level undergranduates and beginning graduate students.
Klenke, A.. Probability Theory: A Comprehensive Course. Springer-Verlag, 2008.
This book is appropriate for a graduate student. It is very thorough and has non-trivial examples.
These notes cover elementary trigonometry from the unit circle point of view.
Alternatively, you can use the qr code.