By default the Eee comes with Linux and FBReader, and FBReader does not read any DRMed formats. There is always the LIT+ConvertLIT approach, but
eeeuser forums report that the Windows eReader reader software will run via wine. This may make eReader the only DRMed format that can currently be read on all common Desktop systems (Windows, OSX, Linux).
As RCR says, you can also install Windows on the Eee and then you have many e-book readers to choose from. Note that Eee's with Windows XP pre-installed are supposed to go on sale in the US in about a month, see
here.