There are many, many types of books in the world, which makes good sense, because there are many, many types of people, and everybody wants to read something different. For instance, people who hate stories in which terrible things happen to small children should put this book down immediately.
That is the kind of story can expect if you're going to pick up A Series of Unfortunate Events. It's a story that's equal parts sorrowful and humorous; it's subtle and clever; and above all else, it warns away its readers in an amusingly snarky bit of reverse psychology (though I'm sure there are at least a few people who have indeed put down the book upon reading these ominous passages).
A Series of Unfortunate Events is the thirteen-book story of the Baudelaire siblings: Violet, the eldest at fourteen and an amateur inventor; Klaus, the middle child at twelve and a voracious reader; and Sunny, the infant youngest who's a fierce biter and speaks in unintelligible gibberish that sometimes offers the reader clever and hilarious "genius bonuses". The Bad Beginning is, of course, the bad beginning of their story; they lose their parents and their home, and when they're forced to relocate to the first of several less-than-satisfactory guardians, they meet the Big Bad, Count Olaf, a vile and abusive man who wants their fortune for himself.
Unlike some children's series, A Series of Unfortunate Events doesn't pull its punches. Count Olaf isn't abusive because he's mean to the kids. He's demeaning, creepy, and outright violent; he hits Klaus, admits that he plans to "dispose of" Klaus and Sunny, and has a pretty damn disturbing sexual subtext with Violet... though a reader might not notice the latter until after they've grown out of the target audience.
It's also a very frustrating story. Does the "Adults Are Useless" trope drive you nuts? A Series of Unfortunate Events is made of useless adults; half the point of the story is that the adults in the Baudelaire's lives fail them utterly and completely, time and time again. And the other half of the point is that you'll never find a happy ending here.
Now, after hearing that, I can see how someone might want to avoid the story. But if I can talk you out of it, let me. These are good books. They're quirky and clever, at times somber and at others hilarious, both optimistic and intensely frustrating, and overflowing with enigma. Honestly, I love the books. See those gold stars up there? Snicket earns them, and I honestly wish I'd read these books younger than I did. I would've loved for them to be a part of my childhood instead of my adolescence.
Of course, they're not for everyone. My mother, for example, couldn't read past the first book, declaring the series too depressing to continue. I don't prescribe to that; I think the story's cathartic. Its characters are forever oppressed and overwhelmed, and they still pull through; the mysteries pile up and answers are slow or even nonexistent, but the emotions are poignant and powerful.
I really highly recommend the series for anyone interested in MG. The Bad Beginning suffers a bit of a plot hole issue--Olaf's plan here doesn't make a ton of sense when you really stop to think about it--but it's a reasonable start to what I think is a strong series, and I definitely suggest giving it a try. If you've got the time and patience, I'd stick with it until The Miserable Mill, at which point the books break the "Baudelaires go to a new guardian" formula and start hinting at the larger plot.