I just bought the game and even managed to get it working, but there is one problem... The second part is missing. In my GOG library I get the option for only one installer, which is supposed to have more than 300MB, but in fact has only around 170MB. It works fine, but it seems to install only Robinson's Requiem. Am I missing something? Has anyone else encountered this problem?

I'm adding to this.

Only see the one 300 mb installer yet once downloaded it is about 177.
Going over the installed files there is clearly only RR related files & dosbox files.

Was wondering if I remembered wrong about Deus being bundled in but it says so on the store page.
Kinda annoyed by this as Deus was my main reason for buying this.

Same here... RR works fine, can't seem to find DEUS.

It's the same in my case. I just bought the Game a few days ago
and i only got the RR-Installer. Maybe GoG has split up the Games
into two Installers and has not yet updated the Site with the Deus Installer.
For me Deus also was the main reason to buy this Bundle, because i own
RR since 18 years and looked forward to get known to it's successor.

Hope GoG will update/fix the Site pretty soon.

Best to send in a support ticket about this.

:)