Welcome Martin, I hope you find everything you need here.
I have a Sony PRS-600, and I love the features that come along with it. Easy to use and has the ability to highlight, annotate, even hand-write the notes onto the page, to name a few. If I were you, I'd go to the Sony ebook site, BooksonBoard, Fictionwise, Kobo (used to be Shortcovers) and see if they have books that you need. Now that the Nook is out I think you can also go to BarnesandNoble.com too, but hold off on that-I think I read somewhere in the forums that u can buy the book but cannot put it on the Sony (don't quote me, I'm not sure!). See what different stores offer and if they have a wide variety, I don't see what would hold you back. Good luck!