Now how could an eBook application possibly borrow anything from an action/RPG game?  Let's back up and I will explain what makes Dark Souls an unique experience:

While Dark Souls is mostly a single-player game, it is possible for players to write orange messages on the ground that other players connected to the internettings can see.  These messages can be created from a set of pre-determined words to help a player out such as "Tough enemy ahead" or "Use ranged attack".  These sorts of hints can make all the difference given the crushing difficulty and death penalties inherent in Dark Souls.

Some messages can be a bit vague

I think Kindle could really use something like this.  Already Kindle lets you know if other people think a passage is particularly important:

And Amazon Kindle also allows for you to write yourself notes into the text:

So why not allow your notes to be seen by other people?  Now this feature could be used for evil; "Snape kills Dumbledore" on page one of Harry Potter and the Sorcerer's Stone comes to mind.  But I really think notes in books would be useful in non-fiction anyway, so there's one restriction.  The message function could also become abused in political books regarding current events or (the now standard) politician memoir, so those would also be restricted. 

In Dark Souls you can also give other players intentionally false or misleading information, which in some cases adds to the already high tension of Dark Souls.  However in Dark Souls players also have the ability to vote up or down a message.  In the case of Kindle you would be able to vote up or down a message depending on how useful/factual you think the note is.  It would be possible to get fancy and Amazon could apply algorithms on user accounts to restrict their number of messages if a specific user keeps producing down-voted notes, and likewise increase the cap on users whom have a track record of beneficial notes.  (A good user "levels up" as it were).

It's been a while since we had a pretty picture.

Another aspect of Dark Souls's message system is after a period of time, a message expires.  So even very useful information will have an expiration date.  I can only assume one of the reasons is to keep new players contributing to the message system and to keep the floor of the levels from being flooded with orange!  Now this system wouldn't necessarily have to be adopted by Kindle but perhaps if a message does not receive a certain number of votes based on how many users have purchased the book then it will expire.

I hope Amazon or another eBook format jumps on this or a similar idea.  Harnessing the time and expertise of the readership to improve the experience of using and reading a textbook or how-to manual or even a cookbook by slightly improving on existing functionality seems like a no-brainer.  I will leave you with one more thought on Dark Souls before I leave:

In Dark Souls, bonfires are your save points which also increase your health.  At the bonfire you may also use up an item in order to increase the health of you and anyone else who uses that bonfire for a time.  The action you perform is to Kindle the Fire.