O'Reilly - Top 2013 ebooks and videos for 50% off (opens in new tab)

http://man7.org/tlpi/purchase.html

I didn't end up doing as much Linux C programming as I expected but for the little I did I found the ebook version more useful -- the paper book is hefty and doesn't travel well. It looks great in my bookcase next to Knuth's TAOCP though.

O'Reilly seems to source their ebook files from the original publishers so I assume their version is identical.

This particular item costs 40 tokens to download. That's pretty pricy; IIRC additional tokens used to be US$10 for 5, making that approximately an $80 purchase.

As the previous sentence touches upon, Safari used to allow subscribers to purchase additional tokens. IIRC they discontinued this a few months ago; now, you get so many tokens per month, and that's it (5, at the unlimited access level).

I have no affiliation with O'Reilly. But I describe this both because it is an ebook source for the title you mentioned and because O'Reilly was one of the earliest and most consistent supporters and providers of DRM-free ebooks.

It's unfortunate that their "model" and practices appear to be "shrinking" or becoming more constrained. No longer can one buy tokens in order to acquire additional titles. For example, I have several Addison-Wesley titles that I acquired through O'Reilly Safari tokens, DRM-free.

I guess now we're increasingly stuck with Amazon and the like, where our "purchases" are DRM-ed and subject to constraint and "revocation" at the whim of the powers that be.

O'Reilly still allows DRM-free purchase of their own titles (outside of Safari). But other publishers are perhaps heading in more restrictive directions.