Welcome aboard! Sorry for the bum info you got, but don't pitch the 900 yet.
You can certainly buy books from Sony directly from your 900 using the "Store" tab on the home screen. You can also obtain books from a variety of other sources, both for free (public domain) and paid, but you'll have to use your computer to buy/download them them move them to your Reader. Check out this thread for starters:
https://www.mobileread.com/forums/showthread.php?t=11052
Finally, your local libraries may let you check out ebooks. Your 900 will most likely be able to view them after you've downloaded them to your computer, using the free Adobe Digital Editions software. Check the website of all the libraries where you have borrowing privileges to see if they have ebook lending (be sure that you don't get this mixed up with audiobooks!). If they lend ebooks in either ePub or secure PDF formats you should be able to read them on your reader. Check out this thread:
https://www.mobileread.com/forums/showthread.php?t=27631
Cheers,
Bob