Until January 6, that is!
Both books are written by Stefan Kottwitz. The LaTeX Beginner's Guide came out in 2011, and I still consider it as a very valuable book to newcomers — e.g. a useful tome to assign your new research student as prerequisite research-skills reading. (You can read my review of it here) (whoa where did I find the energy to write such long form back in the day?!)
The LaTeX Cookbook is actually still quite new, having been published just a couple of months ago in October. (Which makes this deal even more amazing, especially with the currency situation in this part of the world right now…) Anyway! amazing deal or no amazing deal, this book is another one in the “keeper’s” category. Kottwitz continues his style of accompanying lots of useful code with an equally illustrative amount of explanations and best-practice tips. You know how some cookbooks are all “You want to do this? OK take this code” without too much explanation? This isn't one of them. So in a pinch, you may be thinking “why can't I just slap this code in and get it done with” (well actually most code in this book will do that for you anyway), but trust me, you’ll learn much more about LaTeX if you spend a few minutes reading. It’s written in a very easy-to-ready way anyway.
This book doesn’t beat around the bush with introductory material much, but digs into all the interesting things that you’ve probably wanted to do after writing up that first paper with LaTeX, or for writing up your own thesis or book — How do I change the fonts exactly the way I want? Can I draw my circuits/plots/chemical diagrams/flowcharts in LaTeX now? (Yes I enjoyed the chapter on Creating Graphics a lot — in fact you can download it as a sample chapter!) Mmmm you think your doc needs some pretty decorations, let’s see how we can spruce it up — Ah! Ornaments, coloured lettrines, images with rounded corners or badge-shaped, so designer-ish! (Come on, admit it, you know when those creative/productive procrastination mood hits…)
Another chapter worthy of mention is on how to ask a good question, and formulate a minimal working example (MWE), to make it easier for others to help you solve a problem. Having lectured students myself, I cannot emphasise enough how important this skill is. *meaningful nod*