Gamebooks

Gamebooks are a strange invention. When I was young, the Fighting Fantasy books were one of the coolest series I read. Playing The Warlock on Firetop Mountain again on the iPad, I realise that:

1. It's not well written;
2. It has a labyrinth that's impossible to escape without mapping the whole-damn thing (no wonder I thought the book was broken when I was a child);
3. It's focussed on physical movement from room to room (Why? Choices can/should occur at any point in a narrative.);
4. Most choices aren't really choices at all. "You may go east or west." But there isn't any hint, any decipherable reason to choose east over west. The story might as well have been linear.
   

Gamebooks are still with us. Computer role-playing and adventure games contain decisions through dialog trees. RPGs, like the D&D red box, occasionally feature gamebooks.

My questions are:

• Why have gamebooks remained in the amateur and children's area of literature?
• Why hasn't a competent author written a multi-pathed novel?

Ever since Borges and Cortázar, no really good author seems to have gone close. It's a shame. How about a murder mystery, where the reader has to piece together clues found in branching decisions? I'd read that.