
https://www.amazon.com/Investment-Science-David-G-Luenberger...
As an initial focus, I suggest understanding discrete time models well. If you've got some LA and calculus then I'd suggest just hoping into Introduction to Mathematical Finance by Pliska. It's concise, zero filler, but really clear.
Varian, 'Intermediate Microeconomics' Luenberger, 'Investment Science' Wooldridge, 'Introductory Econometrics'
for the undergraduate background and then at the graduate level Jehle and Renyi for microeconomics, Duffie for asset pricing theory, Tirole for corporate finance and Campbell, Lo and Macinlay for econometrics.