No it probably isn't. But there is quite a good argument for the expensive verions: not being tied to a platform.

Isn't it also freely available? http://graphdatabases.com/

1) I've seen numerous times a similar nonsense scenario where the hard copy is considerably less than the e-copy. Obviously it makes no sense that an e-copy which has no physical costs is MORE than a hard copy. (I've also frequently seen the same thing with movies/tv shows, where the disc based copy is less than the digital download copy).

2) This is a perfect example of what Amazon is doing to kill competition and why the gov't case against Apple is so misguided. They're actually helping the real monopolist (Amazon).

@Jon you seem to misunderstand the Apple case involving EBooks. Apple colluded with publishers to artificially raise the price of EBooks, this is illegal. This is why nearly every publisher is rolling over, they knew they got caught with their hands in the cookie jar.

Amazon on the other than is using their market weight to drive costs DOWN. That is always legal. Lower costs are good for the consumer. Might this have negative impacts on other companies? Sure. But antitrust laws are for protecting the consumer, not companies from disruptive forces.

As a whole I am against government regulation for most problems, however the antitrust laws the US has are some of the most important regulations we have on the book. One thing that irritates me immensely is watching Apple truly do what Microsoft was allegedly doing back in the 90s, and Apple getting away with it. The antitrust lawsuit Apple deserves is stratospheric for their categorically illegal position that an application in the iOS store cannot duplicate native iOS functionality. THAT is monopolistic.

Does this mean that you're looking at creating a graph API on top of Raven again?

An advantage to purchasing from O'Reilly is the availability of three open-format versions, which suits whichever devices you wish to read the book on. Conversely, the ebook on Amazon is targeted for the Kindle. I don't use Kindle, so a no-go for me.

Related to new interests: the blog series on storage engines has been a great read and well aligned with some of my own interests.

Given the fact that Voron is now well underway and as a relatively general purpose storage engine could serve more purposes than its use with RavenDB, could we expect a revamping of Rhino service bus, potentially leveraging Voron for storage and possibly taking some new ideas from e.g. 0MQ and/or LMAX/Disruptor?

Not a hard one indeed. - O'Reilly books are in multiple formats and drm-free; - Buy one get one, two books on O'Reilly will cost you 50% each. Enjoy your Kindle, though.