That's silly, right? On a regular computer, yes, it is. So why do we accept those sorts of restrictions on our ereader devices? I can't open two books simultaneously on my old Kindle or my new iPad. I have to close the first book before I can open the second.
I know what you're thinking... When you use your Kindle, iPad or other device you're only interested in opening one book at a time. That's fine, but what about being able to open that book in two different places? You've always been hold a spot with your finger and flip to another location in a print book. It's so easy we often do it without thinking. That includes the index, btw. How often do you hold your place in a print book, flip back to the index to look something up, then simultaneously open another page in the book without ever having to close the original page? I do that pretty regularly in print. Good luck doing it in an ereader app.
Here's another common scenario: you're using a cookbook or reading a how-to-guide with step-by-step instructions. There are definitely times when it's handy to be able to flip back and forth between an illustration and the written steps, for example. Again, easy to do in print but impossible with today's ereader apps.
Now let's go back to the "one open book at a time" problem I started out with. What if you're a student and you've got an etextbook as well as another ebook on the same topic. Why shouldn't you be able to open them both at the same time to compare related explanations, diagrams, code, etc.?
I'm amazed that with today's state-of-the-art ereaders, you can't do something as simple as have the screen split into two panes for different views into the same book, let alone having two different books open at the same time.
Why am I highlighting such a simple missing feature? Because it shows just how far we still need to go to implement common print reading capabilities in today's ereader apps. I'm still a huge advocate for richer content models that truly leverage the ereader device itself, but I'd love to see Amazon, Apple or anyone else who's paying attention to build more basic functionality into their apps. As it currently stands, every time I open the Kindle or iBooks apps on my iPad I feel like I'm using a time machine, heading back to the late 80's when DOS was king, only one app at a time could be opened on my 80286 computer, the music was bad and the hair was big.
Living through the 80's once was painful enough. eReader developers, please, oh please bring us into the modern era by adding some cool functionality into your apps, OK?