Introductory book on cell biology
Lot of classic books available, most famous (at least in India) are


Molecular Biology of the Cell by Alberts et al [ Free Online | Amazon ] -- Simple language, good figures and my personal favorite 
Molecular Cell Biology by Lodish et al [ Free Online | Amazon ] -- Very detailed with good examples 
Gene IX by B Lewin [ Amazon ] -- Nice examples and figures. Lessons are in different order than most cell biology books.


If you want to just learn quick concepts, use online resources like Scitable by Nature. Pretty nice information with references and recommended reading.