I didn't think Grey Hat Python was a great book, but it serves a valuable purpose that I'm not aware of another book supplanting; which is that it shows you tha

I didn't think Grey Hat Python was a great book, but it serves a valuable purpose that I'm not aware of another book supplanting; which is that it shows you that you can use underlying programming to do security-related tasks, instead of being limited to just using tools. The widest chasm that separates security professionals is the one between those that can only use tools other people provide and those that can write their own tools. And more than just being able to write them, but being able to write them quickly enough to be of use during an engagement (which usually only lasts between 1-3 weeks). A lot of security testing at the non-entry level is putting together specific tools to accomplish an engagement-specific task. You don't generally spend a lot of time building giant edifices, it's usually lots of small things that you mostly throw away between gigs (minus whatever underlying libraries you favor using as construction components). In that regard, I think Grey Hat Python is still a good book to introduce you to the idea of using real programming to do hacking, even if you never write a line of Python on an engagement.