Is there no manual for the game ?

I don't know, but you can find it googling on a website called mocagh.org. The links I post are not working.

Thanks !

FYI, the GOG version has the game manual (look for a pdf in the game folder), but the copy protection seems to be MISSING. Fortunately, MOCAGH has it scanned:

www . mocagh . org / broderbund / uukrul-amulets.pdf

maybe because it's not necessary anymore and you can insert any random value to pass it?

Not to mention it was a pain in the butt to use (I understand the reasoning for it, if photocopied the page would be black, but still). Black text on dark maroon paper is heck on the eyes!

FWIW, the copy protection info originally needed is in the installation folder in 2 files called "Amulets-1-2.jpg" and "Amulets-3-4.jpg".

The copy protection appears to be disabled anyway, so it doesn't really matter.

manual is in the games root directory ( for example c:\gog games\the dark heart of uukrul ) file name is manual.pdf

It was already mentioned above, but if you use:
 * https://www.mocagh.org/broderbund/
you see a lot of files - scrolling down to "uukrul*" there are these 6 files.
   uukrul-amulets.pdf 2013-09-17 05:04 527K # old copy protection not needed with GOG version
   uukrul-back.jpg 2000-11-23 04:52 482K # Back of original package
   uukrul-disk.jpg 2013-10-06 05:08 179K # Image of 5 1/4" disks ;)
   uukrul-manual.pdf 2013-10-06 22:32 17M # Scanned manual
   uukrul-note.jpg 2000-11-23 04:58 136K # A yellow note from original work ...
   uukrul.jpg 2000-11-23 04:51 394K # Front of original package
Just for the curious ... and those who want to have those ...
The manual under Linux is in "./game/data/Manual.pdf" for current directory
"." being the install directory incl. start.sh.
Invoking here
   ln -s ./game/data/Manual.pdf
makes a link to this manual - which is 61 MB (compared to the other above
being 17 MB and incl. both empty pages ... keeping page numbers ... ;)