By all accounts this is the whale devouring the minnow. Overdrive has thousands of retail partners and over 18 thousand library partners, while Booki.sh has a staff that you can count on one hand. You can count Booki.sh retail partners on both hands (9), and they just signed their 50th publishing partner (mostly Australian, I think).
I've been watching Booki.sh since I first heard of it in October 2010 (an early version worked in the browser of the K3), and I think it is a fascinating experiment in cloud reading. On a related, I covered it in some depth when it left beta back in November 2011. The platform differs from most in that it is entirely based reading in the browser. While Amazon and other experimented with the idea, Inventive Labs went whole hog and based their platform on it.
While it's widely called a cloud based reading platform, that is not quite true. When it was first conceived, Booki.sh was dependent on a live internet connection. By the end of the beta program, that had changed. It is still built upon HTML5 based browser reading apps, but it also supports offline reading.
So what does this mean? First, OD isn't one to be written off. They might be losing the support of major publishers, but they can still innovate. And it looks like they know when to buy the tech that they don't have time to develop internally.
This move also suggests that a number of parties believe that cloud reading (and HTML5 based cross-platform apps) is going to be the key tech this coming year. Safari bought ThreePress (makers of the Ibis browser based reader), Amazon launched the Kindle Cloud Reader, and even Kobo has announced plans to have an HTML5 based reading app.
It seems that platform specific apps aren't expected to stay round, while cross-platform HTML5 based ones are. I tend to disagree, but I'm looking forward to watching it play out.