[rwizard]

Ideally, for PDF's you would want a reader with an 8"+ screen; however, since you will be primarily reading novels this may not be as necessary. (Especially if the scientific journals are primarilly text with few images. Although depending how they have been formatted, your milage on a smaller device may vary.) I personally like the looks of the nook and would recommend checking one out in the store (once the stores have demo units in) before buying something else (this is what I am doing).

That being said, there are allot of books available in epub from a wide variety of sources, most using Adobe's DRM. (The exception being Barnes and Noble but thier DRM is getting added to the Adobe software so as long as device manufactures include the newer version of Adobe's software in a later firmware update the Barnes and Noble ebook store will be another resource for all readers using Adobe's software). Because of this, any reader that supports Adobe DRM'ed epub books (which Sony does) will have a substantial selection to choose from (you may have to look around for the book you want a little more than the Kindle with Amazon though).