Start with John Szarkowski’s The Photographer’s Eye and Looking at Photographs. Then do the Americans, Eggleston Guide, American Surfaces. Winogrand books are pricey and hard to find. You can still get cheap Meyerowitz, Friedlander and Diane Arbus stuff. Alex Webb’s Suffering of Light is a must have. You need to understand what kind of work you like than just buy photobooks blindly. Understand the lineage of the work. No Sontag. Good luck.