Best PDF Reader for Nexus 7

I'm looking into getting a Nexus 7 and one use that I am very interested in using it for is to read some textbooks I have in PDF format. What is the best PDF Reading app i can get that will allow me to flip through the pdf text books like a book? Also if there is anyone that does a lot of reading, how do you find reading books on your Nexus 7? Is the screen too small?