Looking for PDF books suppliers

So, after my wondering about getting a Sony Reader, I actually ordered one today. On eBay (without laser engraving) as Sony’s shop doesn’t have it available anymore, and I’d rather do it sooner rather than later, as you’ll never know what might come up when you plan too far ahead.

The main use will certainly be to read the common PDF reference documentation as I’m plenty of that, and I often end up either printing it or not using it at all. Give me a few months and the amount of paper I’d be saving would be worth the money I spent on the reader 😉

But there are other books too; Pragmatic Bookshelf sells PDFs for books, and they have quite some interesting titles, so that’s also quite a big improvement.

The only thing that would be missing would be O’Reilly books (I don’t have many, but I’m interested in some from time to time, like the GNU Make book I linked before too. Sure I can live without them as PDF, but if possible, I’d like that option too 🙂 For what I can see, they don’t sell the whole book as PDF on the standard store, you can buy chapters at $4, but that’s quite too much for a whole book.

Luca told me to look for the subscription option, which I suppose is Safari Book Online; it sounds interesting, but considering its cost, I’d rather be sure first if that subscription is what I need. So the question here is for hoosgot a Safari Book Online subscription already. Are books in the library downloadable as PDF? Or are chapters downloadable one by one?

Thanks in advance for the info.