Oh man, if you love the slow-burn merchant vibes of 'Spice and Wolf', this question hits home for me. I dug into collecting the series a few years back, and here's the practical scoop: the official English-language light novels were published by Yen Press in single volumes, not as one giant, neat omnibus run. What does that mean in practice? You can buy each translated volume of the light novels individually from bookstores or online retailers, and Yen Press did release special digital bundles at times, but there isn’t a single, comprehensive omnibus hardcover set that collects everything at once in the mainstream US/UK market.
That said, don’t confuse the light novels with the manga. The manga adaptation illustrated by Keito Koume has seen two-in-one omnibus-style releases (Yen Press packaged the manga in bigger volumes a couple of times), so if you’re hunting for bulk physical reading, the manga gives you more bang-per-book. Also, occasionally publishers do reprints or special editions and online retailers will bundle digital volumes, so availability can shift. If you want the novels in bigger chunks, keep an eye on sale pages for phrases like "2-in-1" or "omnibus" and check the ISBN numbers against Yen Press’s official listings.
In my experience the safest route is to monitor Yen Press’s site, set Amazon/Barnes & Noble alerts, or scout local used-book shops and eBay for older prints. I snagged a couple of rarer volumes that way and it felt like treasure hunting — plus, rereading Lawrence and Holo while flipping through physical pages is a little ritual for me.