So here's a modern Greek perspective to add to the choir. In modern Greek zero is indeed plural, you would say 0 βαθμοί for example to say 0 degrees. However, in contrast to English:

1.5 books ενάμιση βιβλίο -- singular!

You are functionally saying something closer to "a book and a half" in english I guess! Actually this is an interesting duality in english: 1.5 books but a book and a half. Guess it depends on how "separate" linguistically the numbers are: is it one book and a half book or is it a single quantity? Greek for decimals between 1 and 2 picks the "two quantities" approach.