Anita's book suggestion is the best one if you're looking to risk buying on eBay, flea markets, or car boots, for less than a $100 a piece and occasionally up to $500.00, and double that if you're going to buy from a store, on line or real. I'm not sure I would stand by those precise figures. Probably what I mean to say is that if you are wanting to spend less rather than more.
It then depends on what your interests are and how much you are willing to spend. To get a sense of what good 20th C. Murano can look like (in a book, anyhow) I'd start with Marino Barovier, 'Venetian Glass." It's small, but it's cheap, quite unusual for a book on glass. For information on Murano techniques, there's Marc Heiremanns, "Murano Glass: Themes and Variations,' on the history of the companies and the glass makers, there's Clark Gable, 'Murano Magic,' and, if you're going a little more upscale and focussing on a particular, but relatively less pricey company, there are Pina's books, 'Archimede Seguso,' and 'Fratelli Toso.' I've also got a few books because looking at the photographs of the glass is the closest I'll ever come to owning the glass. I don't think there are too many bad books on Murano glass, just some quite expensive ones where you wonder if you should have bought a piece of glass instead. I will say, however, the more books I've bought, the fewer mistakes I've made in my purchases.
I don't think that there are in and out companies. Murano glass encompasses a range of styles and prices, and, ultimately it boils down to what you like. For example, Anita and I both love Murano glass. But if we were each to pick our favourite 20 pieces, there would some overlap but some very different pieces. That's one of the reasons I like Murano.