Book where RPG characters are portrayed as real

Question

I'm looking for a Book where RPG characters are portrayed as real. Then at the end it shows that the RPGers are being played by another nested reality of RPGers and there is a bomb in the room.

Other random memories:

• One RPG character winds up wounded and with centaurs.
• An RPGer tries to scratch off a river hexagon with a butter knife but it refills.
• One RPGer tries to quit but his car won't start for him to leave.

I don't have much else. The cover was blue and showed a basket being lifted into the sky. And I keep googling game end etc. (it's not Ender's game!). I only remember those few scenes and that it's old (80s, maybe as late as 90-92 but I don't think so).

Answer 1

Gamearth by Kevin J.Anderson. It is a trilogy and there is a (brief) Wikipedia article describing the series here.

The scratching off a river hexagon is when they players are trying to remove it from a map:

The hexagon of a lone village was inundated and changed without a trace. Melanie thought of the villagers, the people, their homes and fields.
The River moved on until it emptied into the sea below.
Melanie sat frozen. David turned gray.
Scott jumped up and ran into the kitchen, pulling open drawers until he found the silverware. He came back to the map with a butterknife. He chipped away at one section of the new blue color.

As mentioned in a comment the cover is blue and does show a balloon basket:

You mentioned in a comment that you have been Googling game end, and indeed the last book of the trilogy is called Game's End.