Unbelievably Simple Role Playing (USR) system by Scott Malthouse, then you should. The system does exactly what it says on the tin and provides a simple yet versatile system in just 9 pages. Indeed, the thing I found most difficult about the system was trying to spell 'unbelievably' correctly.
When I saw the system, I decided that it was also a good system for a gamebook (simplicity and versatility being key to gamebook systems) so I wrote a short solo for it called Locket Away. Scott describes it very well:
You play as a hard-boiled detective in a fantasy realm on a hunt for a mysterious locket that belongs to the beautiful mistress of Prince Talos. Thrilling brawls, seedy locales and strange denizens await you on this investigation into the heart of Jailton.
My aim with this solo was to highlight different aspects of the USR and its versatility in a short solo.
So what are you waiting for? Both the brilliant USR and my solo are free! and merely a few clicks away.
You can download the USR here.
You can get Locket Away here.
Take a look at Scott's blog (which contains more great USR stuff amongst other wonderful things) here.