XKCD, for the uninitiated, is a webcomic "drawn" by Randall Munroe. It features primarily stick figures and typically focuses on "nerdy" topics such as science, math, science fiction, Firefly, and the like.
XKCD: Volume 0 is the first collection of XKCD strips. Munroe selected the best of XKCD from the first 500 or so comics. He added a little commentary to a few strips and included some coded messages, which I didn't bother decoding. The book will no doubt delight XKCD fans.
I used to love XKCD, chiefly for obscure jokes about esoteric topics. (I am also a nerd.) However, over the years, the quality of XKCD has significantly degenerated. Relationships and sex have always been a theme of XKCD, but strips on this topic have gotten progressively creepier and more disgusting, culminating at last in the infamous "TGI Friday's" strip, the point at which I stopped reading for enjoyment. (I'm not providing a link because it is extremely NSFW and doesn't have even a vestige of humor to make up for its coarseness. If you really want to know, it's #631.) (I say "for enjoyment" because I did continue to read for several more months to watch the train wreck, but eventually, even that amusement paled. I haven't read xkcd for probably close to a year.)
In addition to the proliferation of "sexkcd" strips, the math/science strips have also declined in quality. The complexity has declined to high school level at best, and the jokes are no longer clever but are instead "reference" jokes, by which I mean that they are predicated on Munroe and the reader sharing the same bit of obscure knowledge and being contemptuously amused that other people don't. (I must shamefully admit to having laughed at similarly premised "jokes" in the past.)
Munroe's disdain for the liberal arts has also grown significantly, or perhaps is merely showing more. I'm an engineer myself, but I highly value the individual study of liberal arts, particularly in terms of what used to be called the classics. Munroe, on the other hand, has nothing but sneers for any academic pursuit that is not math or science. In one particularly egregious example, he made an offensive comic, then doubled down with an offensive mouseover text that stated outright that people who are "not getting a real science degree...have a lot of free time." This statement, particularly in context of the offensive comic, made clear the depth of contempt he has for the "soft" sciences. Hours later, he added, "Zing!" to the mouseover text, in a stealth edit apparently intended to soften his insult. The damage, however, had been done.
In short, as Munroe's mask has slipped and the ugliness of his personality has shown through, I have stopped reading XKCD. Unfortunately, his behavior has also colored my reaction to the original comics, to the point where two stars were the most I could conceivably give to the book. Looking at other works to which I've given two stars and my admittedly arbitrary choice to rate books based primarily on my level of enjoyment (except that I will give five stars only to a book that I consider objectively excellent), however, I will decrease the rating to one star.