Whether this helps or not,...I exit out of eReader on my N800 by doing the following,....While in eReader I first tap on the Home icon on the Palm taskbar. This takes me back to Palm's menu screen. I then get out of the Palm emulator by either hitting the Esc key on my N800 (I'm guessing you have an N900 so possibly the backspace key might work since you don't have the Escape key?),....or by hitting the Home key on my N800 which pulls up the current running programs and then tapping the 'x' on the Palm emulator program box. This then gets me to the Garnet VM launcher menu (or xTerm command line if launched by command line).

BTW, the only time I have found that I have to re-authorize my books is if I run eReader through the command line and then the next time run it using the Garnet VM program launcher (or vice-versa).

Just saw this tip by Michal Jerz over on the My-symbian.com forums (http://my-symbian.com/forum/viewtopi...40793&start=12). Maybe this will help since you don't have Esc key on N900...
'And it is actually possible to switch Quake (or any other fullscreen app) to "windowed" mode when you want to close it. Press the Power button (to show the menu (which contains the "End current task" button) and just WAIT several seconds. Status/title bar will be shown in the backround. You can close the menu and normally end the app using its "X" button.'

I tried this on the N800 by putting the Palm emulator in "windowed" mode by cycling through the different viewing modes (landscape, portrait, windowd) using the N800's full-screen key. Once in windowed mode, I wwas able to hit the 'x' button on the window and close it that way saving the settings. Hopefully tapping the 'x' button in windowed mode will work for you too.