The problem with books on glass is threefold: first, they're expensive, and, second, they're seldom either completely accurate or comprehensive, and third they're either absurdly general or arcanely focussed. Despite all this, I find that I was far worse off with no books, and I've spent a fair bit on glass books. I've got all the books mentioned, except Dansk Glass, where I have Lutken Glas ist Liben (yes, in the German as it was the cheapest I could find).
If you are starting to collect Scandinavian glass generally, I'd still get the Pina books. She does make a couple of mistakes, but there's a fair bit that comes up on eBay that I've only seen in her books. Later on, you can focus. If it's Orrefors and Kosta you like, Swedish Glass Factories by Ricke and Thor is the most indispensable, but very pricey. All the other books mentioned are definitely worth buying as you go along.