The standard modern textbook in cell & moleular biology is "Molecular biology of the cell" by Alberts et. al. I can also recommend "On Growth and Form" (Thompson) and "Medical Physiology" (Boron and Boulpaep) as being especially well-written and comprehensive. I'm not sure what books are used for plant biology...
What level is your understanding of biology and are there any areas you are particularly interested in? Alberts as Andy says is pretty standard though it focuses on cell biology and biochemistry.
Good, thank you. I'm getting a copy of Andy's and perhaps the others. I am particularly interested on neuroscience, mainly interested in understanding how our brain processes the vision. What are the good books for this?