There are few ways you can get eBooks on your PSP. One way- you can turn the PSP in to a web browser and hit a HTML page that has an eBook, but an easier way is to use a print utility called PaperLess printer to make images of any printable file or PSPPhoto which makes photos that are properly sized for the PSP. Here’s how to make eBooks using PaperlessPrinter from GameFries, here’s where to get PSPPhoto and here are a ton of great digitized Manga for the PSP. Last up HowToons on my PSP!
