[TakeTheLeap]

It really depends on your professors. You have to learn which ones expect you to read and which ones don't have expectations that are as high.
For example:
In my "Distributed Leadership" course, my professor puts the powerpoints online, and the powerpoints are a summary of the reading we were assigned. We do have some collaborative activities dealing with the readings on occassion, but we are able to pull our book out and reread and have plenty of time to look over things before we have to present findings or discuss.
BUT in any of my reading instruction courses, we had several textbooks to read as well as articles. Her exam questions were usually ones that you could only answer with information from the textbooks and articles (as well as application), and our assignments (lots of projects!) all had reference to something in the reading. In class, we did a lot of discussion about the texts and she expected us to read in order to participate.

It's a matter of weighing the expectations for your classes and reading the most important materials first. From there, you can make decisions about what other classes you should read for and where you can get away with not reading.