I'm guessing you're having trouble because you're on 64 bit linux b/c >currentyear, but beamdog and other developers insist on programming for 32 bit linux even in this The Year of Our Lord Two Thousand Seventeen.

I was able to play after running the following command in terminal:
sudo apt-get install libjson0:i386

If that doesn't work you can access any error messages being thrown by running the executable script from a terminal line, instead of clicking the icon it installs on your desktop. Right click the icon, go to properties, and look at the "Command:" field to see where the executable script is on your machine.

linuxvangog, I hope this packaging can be improved in future GOG releases.

In several previous GOG releases (e.g. Icewind Dale: Enhanced Edition), you bundled too many libraries with the game... including libstdc++ and libxcb-dri3 (which break 3D rendering on systems with Mesa-based graphics drivers if Mesa is compiled against a different version of them), and things like libX11 (which is nonsensical because every desktop Linux system already has it).

But now, with Planescape: Torment: Enhanced Edition you've erred too far in the opposite direction, by bundling no libraries - not even things like libjson or libssl of which many Linux systems don't have the required version installed by default, and which you could have bundled without causing problems.

The optimal solution lies in the middle: Don't bundle libraries for which bundling causes problems or which are already installed on pretty much every Linux, but do bundle the remaining ones.

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Also, please insist that game developers include both 32bit and 64bit Linux builds of each game's executable, and make the ./start.sh script choose the correct one. Shipping only 32bit builds in 2017 (when virtually all Linux gaming rigs are 64bit) is kinda embarrassing, and exacerbates the library dependency problems described above because it makes it less likely that a given library is already installed on a typical system, and also makes it more difficult for users to identify and install the correct package to provide the library.