It’s pretty prestigious, although it’s not really for the best library so much as, you know, a fuzzier idea of the “library of the year” - most improved, unique services, plucky, that sort of thing. I can’t find an explanation of how Library Journal decides in a really brief search (I haven’t gotten that issue yet, as I’m dead last on the internal routing list) but my understanding is that it’s sort of a holistic approach to an award - they’ll point out some specifics, but overall it’s sort of a “doing the best with what they have for their patrons” thing. When we won, the article stressed the money the library’s been able to raise in a state that’s hardly known for great library services. It’s probably also highly political in library-world; everything in library-land gets into library politics, you don’t even want to know.
So in other words, yes it’s very prestigious, but it’s more qualitative than quantitative in measurement. Otherwise the New York Public Library and the Library of Congress would have to take turns every year.
I’m sure the article will be available for you to peruse at your leisure at, guess where, your local library.