On a Quest for the Perfect E-reader

Introverted book-lover seeks compact gadget to contain her ever-growing library.  Gadget should be easy on the eyes and the wallet.  Should also be slim and portable.  Must be cross-compatible with other e-reading technologies in case book-lover gets fickle and decides to upgrade gadget to something new in a few years.  Gadget should also feature some sort of note-taking or comment-writing function.  Wireless technology and sizable storage space a plus.