Strangely enough, ALT+TAB does not work in this game - even though it did in both of its predecessors.
Even stranger, the game runs perfectly in windowed mode - though that's not what I want.

I can force switching out from the game with CTRL+ALT+DEL (bringing up the task manager), and going back to the desktop and read my emails. I can even go back to the game, but the game no longer responds to keyboard events like moving the camera, ESC, etc

Any fix/workaround for this?

Thank you!

For Alt-Tab not working, it is possible that GOG wrapper is disabling it. Take a look at the registry (HKLM\Software\WOW6424Node\GOG.com\GOGUFOAL or something like that) and see if the flag is set to false. As for the keyboard not working when you return, it is possible that either alt and/or ctrl are still registered as pressed, so when you press Esc the game thinks you are press Alt-Esc, thus not respond. Tap alt and/or ctrl and see if it fixes them.

I don't have the game installed atm, if these don't help, do tell me and I'll install it and see if I can find anything else.

Thanks for the tip. No, it is set to 'false', so it's not disabled by GOG at least.

I've tried a lot of keyboard combinations, but nothing seems to kick the game back into reacting to the keypresses.

I'd appreciate if you could have a look.

Thank you!

Installed the game and I also couldn't return to desktop without using Ctrl-Alt-Del. I was also able to alt-tab out if I run it in windowed mode, just like you said in the OP.
Unfortunately, I wasn't able to reproduce the keys not being recognized after Ctrl-Alt-Del out and returning. All keys were still recognized normally.

Best workaround I can suggest for now is windowed mode along with one of the borderless windowed methods suggested over at PC Gaming Wiki.

Yeah, this is how I ended up playing it. A bit disappointing because it's not an old game (pre-Windows-XP) at all.

I have own solve - leaving something in the background like music player (especially Foobar because isn't hunger for resources or power) then you can alt+tab without issues.