I bought my "Book" back on Black Friday and have been pretty satisfied with it as my first e-reader; but that is all I use it for - reading books. I'm not setup with wifi in my house and I've heard mostly poor remarks on the browser performance. But if you're having success with those functions that's what really matters.
Yes - the manual is almost useless, it's decent as a 'quick-start' guide but not what I would call a true user's manual. As for transferring books to the device you might be missing one of two steps: 1) start the u-disk function on the device; 2) connect to your computer via hard-wire USB and use Calibre (which should have come with The Book) for transferring the books. You could try just #1 with wifi, it might work, as I said I don't use wifi.
Also, I've always transferred books to a separate SD card in the device and left the internal memory just for the pre-loaded books. The SD card and the device show up separately in Calibre.