Please note that the domain psp.manybooks.net is (from March 2012) no longer maintained, but you can still use the regular site to read books on your PSP!
ManyBooks offers a large library of ad-free eBooks that can be downloaded for free and read on your PlayStation Portable. Have a look at our Genres page to find something that strikes your fancy.
Below are a few different alternatives for how to read the books on your PSP.
This method is probably the easiest one as you don't need to download any additional software.
This method is fairly quick but does come with some drawbacks. You might have problems with running out of memory if the ebook is too large. You might also find that it is not very convenient to scroll through the book to find where you were last if you should take a break in your reading.
Bookr is a document reader for the PSP which enables native .pdf reading. You need a Sony PSP with firmware version 1.5. Other firmware versions are not supported. To install simply copy the __SCE__bookr and %__SCE__bookr folders to your Memory Stick \PSP\GAME folder.
You can get the software from the Bookr project page on Sourceforge.
Note, the PSP was not built to be a ereader so it will take some effort to make it act as one. In the end you might want to get a dedicated ereader which will give you a much better overall experience. You might find one you like in our eReader reviews section.