DianNC, if you get an SD card - micro SD for the PE - you can load all your books on to that and read them from there if all you want to do is read.
So far I haven't found a limit to the number of books that can be carried this way - I have one SD card with well over 600 manuals and data sheets that works without any problems.
You could also get something like CoolReader for the LCD side and read two books at once
well that's how I have a manual open on e-ink and check data sheets on LCD.