Is there more than 1 type of light novel in the Spice and Wolf series? I've always thought there is only 1 type of light novel for this series (which is translated to other languages).
But I saw on Amazon that they are offering to sell 3 types of the same light novel. 

You can see that below the title section, where it says "See all 3 formats and editions". After that, you need to press the arrow on the left side to see all the 3 novels.

I'm wondering what are the differences between them.
These are just the different cover release versions. At one point, Yen Press was printing these with a slipcover case on them that shows a more "appealing cover" for the Americanized audience. However, not everyone liked this. They're not available anymore and were a limited print only, so the versions Amazon has listed are the normal and slip covered version (plus the one they fulfill, the none slip cover one.)

You can find the original press release here.

I actually own some of these, although I usually display the original Japanese covers as I prefer them. I've attached some photos so you can get a good idea of how they look in real life.

I hope this helps.