This might also be useful for
UMPC's, where a very popular screen size is 7-inch 800x480. I have tried custom sizes on my Pepper Pad 3 and 78x105 and 150x105 mm PDF's both work well using Adobe's acroread (inside FireFox).
Your web pages are generally designed for larger screens (both the navigation pages and the HTML books). Many sites work better than this with 800 pixels in width.
Most UMPC's run some variant of Windows, but the Pepper Pad is Linux, and in general spaces in filenames are a pain in Linux when using the command line. I suggest filenames like Author-TitleWithNoSpaces.pdf. The shorter filenames are probably helpful even under Windows. An alternative is to replace spaces with "_".
Finally, how about a bold font option?