In the "Games" drop down menu there are several categories such as adventure, strategy etc... But there is no category for puzzle games. May I suggest to gog.com that they make a new category for puzzle games. There are many people who like to play puzzle games and it would make it easier to find, and buy, such games if they could be found all together in a group.

There's a wishlist for it that you can vote on. You're not the only one who is looking for that feature to be added.

You can also search for puzzle in the catalog's search field. Here are the results:
https://www.gog.com/games?sort=bestselling&search=puzzle&page=1

What would be a much better solution would be if they would stop pigeon holing games into a small list of broadly chosen game genres and instead assign official tags to games and let users assign their own tags to games which can be either private or public. When Steam added that feature, finding games of a specific type became a breeze as tonnes of gamers out there go and tag everything even if an individual couldn't be bothered. Of course they probably would have to filter out naughty words and whatnot or have some kind of moderation to prevent morons from putting tags on games like "penis!" and whatnot, but Steam seems to have figured out how to do it and it's mighty useful.

Having said that, I'm sure GOG will do something like that in a few years time, but they have their hands full for quite some time to come just getting basic functionality to work. :)

Incidentally, I voted for the wishlist item as it's better than nothing for now.

I admire your optimism.

Oh I'm not optimistic that they would actually do it, just that they'd need to in order to stop morons. Not that they WOULD stop morons. :)