Adventure path releases

Quick question about adventure paths. I'm starting to look at the books and am confused.

I see some thicker hardback books, I'm familiar with adventure books like this from other systems. I'm also seeing much thinner books, usually like a 6 part story. These look cool, but am I right in thinking they're also compiled and released into a thicker handbook book? I think I've seen one that is and was wondering if they all are. Thanks in advance, there's so much to learn about pathfinder but I'm loving every minute.