Most commonly referred to as an "info dump", that is. You have three chances to get a reader to snatch up your book. The first comes when they see your cover. That will be the most immediate draw, and even the title won't be as persuasive as how enticing your cover is. The second comes when they read your blurb. A lot hinges on how well this is written, but the deal breaker comes as they take that little "Look Inside" Amazon provides.
If the first thing they see are two huge paragraphs of block text, you've already made them weary, and the danger is that some will, at best, skim the text to see what on earth you're going on about. IF they turn the page and see more of the same, you've lost at least half your potential buyers, right there. For those that trudge through it, you had better hope that 3rd page doesn't contain even one more block of text. Three pages is simply too long to wait for the action to get going.
You can just about get away with this a little further into the book, after you have the reader hooked. Hooked readers are much more forgiving than ones wanting to be hooked. Master storytellers are the ones that have found the balance of just enough back story, at just the right time. It's never necessary to lay out the entire reason for your books existence in one fell swoop- and most especially within the first 3 pages of your book.
Even if you manage to hook your reader despite the dump, do you really want them telling their friends: "I liked it once it finally got going, but it was hard to get through at times.". Scary words, in my opinion, and not exactly a shining endorsement. Liked and hard should never be used in the same sentence to describe a product, even if they are separated by a comma.
If you're not getting the sales you should be getting despite the data telling you people are looking, you should really try and find out why. If you've "taken a dump" on your first page, you just might want to clean it up. :)