Someone on Hubski (I thought it was you?) mentioned A Short History of Nearly Everything and I remembered that I always meant to read it again. It's fantastic. It's like school but fun. And I forgot enough of it that it's like reading a book for the first time.I read 3 (count them t-h-r-e-e) books about the expanded Star Trek universe. But I still have Georg Joos "Theoretical Physics" sitting here in front of me on the coffee table
Look for the middle ground. After I finished SuperFreakonomics (entertaining, accessible, but not very serious) I picked up something by Kierkegaard and read it on the subway for two days, then carried it a few more days before giving up. I liked the writing, but it wasn't the right ratio of effort and reward for my occasional opportunities to read.