Valley of the Exiles gave me nightmares as a kid, but I kept rereading it. Definitely my favourite Spirou, but probably not a very representative place to start. For that you should go with one of the Franquin albums recommended by Snarky.
Spirou albums aren't all available in English? That seems so strange.
If you want more recommendations, check out The Bluecoats, although its availability in English is probably even worse than Spirou. I would rank it just after Tintin, Asterix, Lucky Luke, and Spirou. I would describe it as Asterix set in the US civil war, to give you an idea of what it's like.
Spirou albums aren't all available in English? That seems so strange.
If you want more recommendations, check out The Bluecoats, although its availability in English is probably even worse than Spirou. I would rank it just after Tintin, Asterix, Lucky Luke, and Spirou. I would describe it as Asterix set in the US civil war, to give you an idea of what it's like.