I have the 2nd edition of that back from 2008.
Any other books I should arm myself with?
Arm against what, exactly?
Now that we have the Internet (things were so much rougher in the early 2000's and before), the importance of having the right selection of books in your personal library has declined somewhat. If you follow the trail of breadcrumbs, you'll invariably find a good, comprehensive collection of algorithm documentation and implementation. Just start on the page for "Quicksort" in Wikipedia and look through the footnotes and links at the bottom of the article's page.
The one exception concerning books I would make is Steven Skiena's book ("The algorithm design manual") which I already mentioned. The first half of the book covers algorithms in general (what are these things, how do they work, how do you build them, how can you tell when there's no scalable/optimal solution for a problem), and while this part is already great, the second half is really crackers.
The second half (modestly labeled "Resources") is a catalog of algorithms, categorized by problem domain. This doesn't sound much, but each section contains a general description of what problems fall into each class and can be solved algorithmically, and then gives a list of hints that allow you to pick the best likely solution for each problem.
This helps to overcome the big obstacle you'll always have when you're looking for a good or better approach to solving a problem with an algorithm: finding one which does the job, and making an informed decision when choosing between alternatives. For example, when you have to sort small numbers of integers, what kind of algorithm will you pick? Will you use heaps, for example, or trust in a recursive algorithm? Which circumstances surrounding your need for a matching algorithm would favour heapsort over shellsort, or even merge sort?
Would you happen to know of any books that you recommend that explain every single feature that was added to C99 with examples? Or a good article on the internet?
I can recommend "C - A reference manual" (5th edition) by Guy Steele & Sam Harbison (well, it's mainly by Guy Steele). It makes for a great reference manual, too, so the title is actually spot on and not just for show