I mostly read books and avoid pdf format, convert it to epub with Calibre converter, if necessary.
For reading e-books, PocketBook 902 is just perfect. But I use fbreader180, not the default fbreader, because it allows me to set very wide margins: > 2 cm each margin.
This way, the actual page on screen is of the same size as a regular paperback book page, it has the same font size (2.2 DejaVu) and has the same number of lines per page, and (most important) the same number of words/letters per line.
Wide margins also make reading words at the edges very comfortable.
This could not be achieved with a smaller screen, such as 602.
Those wide margins made the crucial difference for me. Before installing fbreader180, I read with 902 very little, afterwards (with those wide margins) - almost continuously

The difference is like day and night.
So I suggest to everybody, install fbreader180. There is also a script which makes all the internal dictionaries accessible from fbreader180, so there are no cons whatsoever.
Current version of fbereader180 requires to edit the configuration file on PC to set wide top and bottom margins, but left and right margins can be handled directly on PB 902 in another way, so you can easily fine-tune them to your taste.
Yes, also the history application supporting up to 30 last opened books and allowing to move/delete books is very important to me, as I usually read many books simultaneously, and also try to open various versions of the same book to find out which looks the best.
I know, fbreader180 and history.app - additional software, but they make PocketBook 902 so much better! They make the device perfect. I could not ask for anything more.
Actually,
I prefer PocketBook 902 to real paper books.
Often I have a real paper book but I choose to read it with PocketBook 902 instead.
I find it is easier and more pleasant to read with 902, easier on my eyes.
Some regular books have very small font. Even when the font size is ok, still somehow PocketBook is more comfortable to read.
And of course, additional benefits, such as: no need to search for a misplaced book, no need to search for the page I was reading. Instant access to dictionaries, and dictionaries sometimes are very informative, like wikipedia, to look up various geographical or historical references, etc - when reading a regular paper book I would never dream of looking up such things, but with PocketBook - why not. It takes seconds.