If you have not yet been exposed to harkavagrant.com then I can only surmise that all the time you've spent on the internet to date has been wasted. Go rectify the situation immediately and while you're at it, go buy Kate Beaton's first book Hark! A Vagrant, a compilation of comics from the site with some book-exclusive comics tossed in to the mix.
I first came to know Kate Beaton's work after discovering her "Dude Watchin' with the Brontes" strip, where Emily and Charlotte ogle assholes and when Anne identifies them as such, her sisters respond "No wonder nobody buys your books." This might be her most famous strip and it kicks off the collection, but all of her work is like this -- smart, funny, and rather irreverent. The subject of her comics usually find their origins in literature of history, even if the interactions shown here may not have actually happened. (Case in point, when Tycho Brache responds to Johannes Kepler's suggestion of the earth orbiting the sun with "What if your wife orbits my dick.") Beaton expects her audience to be educated and to pick up on her clues as she's not about to waste time and valuable comic-space explaining subtleties to you. There are the occasional themed strips -- such as her exercise in guessing the plots of novels with covers drawn by Edward Gorey or Nancy Drew novels based solely on the jacket art -- and certain characters will reappear, depending on their popularity with readers. Some of my favorites include Sherlock Holmes and his Watsons, pirate nemeses, and the various French Revolution figures. Because Beaton is a Canadian, folks from the US might do a terrier head-tilt of confusion at a few of the strips, but even those comics will usually result in a chuckled (and a quick trip to Wikipedia to learn something about Canadian history).
For those of you thinking, "I love Kate Beaton's online comics, but is this book full of new ones or couldn't I just read most of it online?" my honest answer is that there isn't a lot of new stuff and most of what's in the book is what you've seen before, but I still think you should buy the book. Tally up the amount of time and the intensity of laughter provoked by her webcomics and I think you'll find that the price of this book is actually quite a steal. I will happily give Kate Beaton money with the knowledge that it's going toward supporting such a fantastic cartoonist. Think of it as compensation for the great amount of amusement we've had as a result of reading comics on her site bundled with a down payment on future work that will be just as delightful. So I hope that if you've enjoyed Beaton's work as I have that you'll go support her and buy her book. Just think -- now Charles Dickens and his simpering heroine fetish will always be on your bookshelves for your reading delight. So hot.