In case you did not know: Packt is giving away free ebooks each day. The main downside is that you can not download them. You have to access them via their home page but on there, you can keep them forever access them on their page as long as it exist.
I have an O’Reilly Learning subscription, and Packt books stand out to me as being surprisingly low quality. The editing is poor (or can be, I clearly haven’t read them all) and with English often not the author’s first language, it’ll show. I’ve also seen books that copy RFCs verbatim, but don’t give credit.
Anyway, “yay free books,” but be prepared for the chance you’ve wasted your time.