I bought the Kindle version of the Just Java 2 book this year and am very happy that I did. Nowadays I read my Kindle books on my Android phone more often than on my Kindle device. Reading the JJ book while in waiting rooms, parking lots, etc. when I have time and am not skimming to find a Cattle Drive solution has taught me many things that we don't use on the drive and reminded me of why we do some things. A good many of the code examples scale with the book and since I am reading for concepts and not at my computer coding I don't care if the wrapping is odd on the code snippets. I've noticed that I can read on the phone for 30 - 60 minutes and don't see a drain on my battery.
I powered through the paper version of jj6 this year and I also believe it is a great book by a great author. Some things towards the end of the book may come short, but compared to what I see us doing at work currently, most of it is still very up-to-date, despite the age of this book and it "only" covering Java 5.
Haven't got an e-reader or Android phone. Perhaps it's worth looking into one for this kind of lit
I must admit though that I don't find myself sitting on trains or in parking lots or in waiting rooms a lot :-)