I totally respect your work, and I get that making the books is a ton of effort with all the layout and sourcing all the diagrams and whatnot, but sharing the book here doesn't seem wrong to me.
I mean, I contributed to the book, but its not like I got paid for the work I did designing or diagramming. I got a copy of the book, but I wouldn't really call that payment. Because I wasn't paid, I think its pretty safe to say that I was donating my time and effort to the COS and the origami community at large. I'm totally cool with that, but if I'm donating my time, COS had better not be some kind of for-profit organization, and the COS convention books had better be intended to better the origami community at large.
I get that selling the book is important for fundraising for COS, and I absolutely think that anyone getting these books SHOULD buy them if they can. But since the books (hopefully) are for the betterment of the origami community at large, it doesn't seem like someone downloading it for free is bad. Since people here mostly seem to actually care about the origami community, anyone downloading the book here probably ACTUALLY can't buy the book, and just wants to use it to learn more about origami.
People who download this book probably wouldn't have bought it anyway, so its not like COS would be losing money. And if even one of these people who downloaded the book here got more involved in the origami community, it seems to me like the book was successful in its goal.
I think sharing books that were written with the intent of making money for the author is pretty morally shaky. Sharing books that were written by a non-profit for the betterment of the community seems fine to me.
And if the COS books are intended to make you money, that's totally bullshit and I'm sure as hell not contributing to it anymore.