I suggest the following approach; Start with some school textbooks for grades 8-12 i.e. Secondary Education. This is more for a refresher course in the absolut

I suggest the following approach; Start with some school textbooks for grades 8-12 i.e. Secondary Education. This is more for a refresher course in the absolute basics. The above can be supplemented with the following books to develop intuition; 1) Who is Fourier - https://www.amazon.com/Who-Fourier-Mathematical-Adventure-2nd/dp/0964350432/ref=sr_1_1?keywords=who+is+fourier&qid=1563268572&s=books&sr=1-1 https://www.amazon.com/Who-Fourier-Mathematical-Adventure-2n... 2) Functions and Graphs - https://www.amazon.com/Functions-Graphs-Dover-Books-Mathematics/dp/0486425649/ref=sr_1_1?keywords=Functions+and+graphs&qid=1563268628&s=books&sr=1-1 https://www.amazon.com/Functions-Graphs-Dover-Books-Mathemat... After this is when you enter undergraduate studies and you have to fight the dragon of "Modern Maths" which is more abstract and conceptual. In addition to standard textbooks; i suggest the following; 1) Concepts of Modern Mathematics - https://www.amazon.com/Concepts-Modern-Mathematics-Dover-Books/dp/0486284247/ref=sr_1_1?crid=3RJG1Q2661MUE&keywords=concepts+of+modern+mathematics&qid=1563269004&s=books&sprefix=concepts+of+modern+ma%2Cstripbooks-intl-ship%2C376&sr=1-1 https://www.amazon.com/Concepts-Modern-Mathematics-Dover-Boo... 2) Mathematics: Its Content, Methods and Meaning - https://www.amazon.com/Concepts-Modern-Mathematics-Dover-Books/dp/0486284247/ref=sr_1_1?crid=3RJG1Q2661MUE&keywords=concepts+of+modern+mathematics&qid=1563269004&s=books&sprefix=concepts+of+modern+ma%2Cstripbooks-intl-ship%2C376&sr=1-1 https://www.amazon.com/Concepts-Modern-Mathematics-Dover-Boo... 3) Mathematical Techniques (i am linking this so you can see the reviews but get the latest edition) - https://www.amazon.com/Mathematical-Techniques-Dominic-Jordan/dp/0199249725/ref=sr_1_4?qid=1563269267&refinements=p_27%3ADominic+Jordan&s=books&sr=1-4&text=Dominic+Jordan https://www.amazon.com/Mathematical-Techniques-Dominic-Jorda... Finally, if you would like to learn about all the new-fangled mathematics your best bets are; a) The Princeton Companion to Mathematics - https://www.amazon.com/Princeton-Companion-Mathematics-Timothy-Gowers/dp/0691118809/ref=sr_1_1?qid=1563270182&refinements=p_27%3ATimothy+Gowers&s=books&sr=1-1&text=Timothy+Gowers https://www.amazon.com/Princeton-Companion-Mathematics-Timot... b) The Princeton Companion to Applied Mathematics - https://www.amazon.com/Princeton-Companion-Applied-Mathematics/dp/0691150397/ref=sr_1_2?crid=2NDD0046R25BJ&keywords=the+princeton+companion+to+mathematics&qid=1563270163&s=books&sprefix=the+princeton%2Caps%2C367&sr=1-2 https://www.amazon.com/Princeton-Companion-Applied-Mathemati... One important piece of advice that i have is to become comfortable with the Symbols, Notation and Formalism used in Mathematics. Most students are intimidated by the Formalism (which is nothing more than a precise form of shorthand to express abstract concepts) and give up on studying Mathematics altogether. This is a shame since it is merely the Form and not the Function of Mathematics.