I have known this book since I was child, when I thought it was brilliant, as it is narrated by a child in the same kind of slang as I used (including the overuse of the word 'corny' as noted by another reviewer, and particularly the addition of "it was, really" after every statement). The theme and story are now classic, of course, but the language and setting haven't stood the test of time and I can understand people finding them irritating rather than charming, in contrast to the film, say, which remains timelessly appealing. The style is not unlike Salinger's "Catcher in the Rye," which similarly, I find, is almost unreadable now. Still "I am ten, and they call me Brat" has got to be the best opening line from a 1950s children book.
So I don't think I would recommend buying this book unless you already know the film (or even the new musical) and want to go back to the source. If you do, however, you will find a very different treatment of the story, which I find well worth the read.