(Late to the discussion)
My favorite Generation Ship novel is "Mayflies" by Kevin O'Donnell.
It's an older book (from the 50s)
The protagonist in this book is a scientist whose body is destroyed in an accident, and whose brain is installed as the central computer of a generation ship.
Thus, the story is told from the point of view of the ship's central computer who must maintain the ship and its systems while watching generations of its passengers live & die.
I'd never heard of "The dark beyond the stars" but I just went to Amazon and the reviews are great so I added it to my Wish List
Re "Time for the Stars" -- I also re-read Heinlein's "younger" books periodically ... they are just such great reads...
How about "The dark beyond the stars"? Not only did it confront the decay of the ship, but it had a unique plot wherein the protagonist "Sparrow" and "The Captain" were given long life and were each "programmed" with a different function. One to lead the ship out, and one to lead it home. The possibility that there may be no other life out there, yet the Captain is driven to continue the journey by the aforementioned programming, drives a great plot that questions the meaning of life, both human and alien. A great read. P.S. Just finished "Time for the stars" yesterday (again)
I remember it also -- it was a brilliant film -- but it wasn't a Generation Ship story -- it only had a small crew and it had only been on its mission (blowing up unstable planets or stars or whatever)that might threaten ongoing human colonization...
...still and all it was a great film...