Several years ago, I tried to read a group novel, a mystery caper by a group of mystery and humor writers, but I didn't finish it. Can't even recall the title. That's not a resounding recommendation for such projects, but perhaps they're not intended for a wide audience, but as an exercise for the writers.
Group stories require writers to continue someone else's plot and characters, and try to keep the story cohesive. The process can be hilarious, surprising, revealing, poignant--or downright nonsensical and silly--but always challenging.
While cruising the earlier entries in the readers' forums at Fear and Trembling online magazine, I re-read a story begun by the former editor, John Kuhn, who posted it in June 2007 with the intention that others would finish it, but no one ever did.
He provided the first chapter; I'm writing the second. After all, a writer shouldn't let a good story go to waste -- but there's no guarantee it'll still be good when I get finished with it. Read Mr. Kuhn's chapter, then come back in a week or so for the next one. After that, maybe someone else will pick up the pen and continue the tale.