[cmbs]

It's because of the mobi format.

PDF files have the page size pre-determined when they are made. If you're trying to view a regular paper size page on a small screen, the whole page will be displayed and it can be very very small text. It can be very hard or impossible to read. I can read some pdf files on my cybook and others I can't. The ones I can read, I have to view in landscape and I see only the top half or bottom half of the page at a time.

Feedbooks provides pdf files specifically sized for reading devices and they work perfectly on my cybook, but that's not what you're going to find at the library.

If you're looking to buy a portable device to read pdf library books you should be looking at something with a larger screen, and something that can read a DRM protected pdf. Harry suggested a Tablet PC.

I guess you missed it when I said I have read that NO EINK READER reads DRM protected pdf files. The cybook doesn't. The files from the library most likely are DRM protected. So to read pdf files from a library you're going to have to use a desktop, laptop, or some other similar device. They are not very good for portable devices, unless specifically made to size for the screen.

Mobipocket files have text that flows so it will fit itself to the screen, regardless of size. It also allows you to change font size. CYBOOK and ILIAD read DRM protected mobipocket files, which is most likely what your library has available. I'm not positive, but I don't think the kindle reads DRM protected mobipocket files. I think any kind of portable pc on which you can run the mobipocket reader should allow you to read DRM protected mobi ebooks.

I checked the Los Angeles Public Library website and they don't have any pdf or mobipocket ebooks available. It's only music, video, or e-audiobook.

edit:
Aapparently I'm wrong about pdf's being read on small screens. DRM pdf's don't work on e-Ink devices, but they will work on handheld pc's and the text may reflow. Read the following posts to learn more.