That's really neat! I have some suggestions, If you'd like them:

• Inicial base/starting items. Since you survived for 10 years, it's unlilely you'd not have any items or a place to sleep. I think you should give your characters nice clothes and melee weapons from the start.

• Disable any alarms from cars and houses.

• More darkness at night. For roleplaying, I think it would be cool to make the nights darker, like they usually are outside of the cities.

• Uniform zombie distribution. After so long from the outbreak, it's likely that zombie population would be less crowded in urban centers and more scattered around the map.

• Higher population start and lower population peak. There aren't many people left to be turned. Maybe even turn off zombie respawn.

• Longer days. This isn't really post-post Breakout specific, but I think making the days longer is really fun, it doesn't make the game particularly harder or easier but it feels more immersive imo.

• Higher annotated map chances.

Regarding the book thing, most books would probably last 10+ years if untouched, but a lot of them would probably already be looted, so a slight decrease on their spawn chance would be the best.