Sim cannot complete writing or resume writing books, even worse now.

Sounds like the writer's block issue: Writer's Block moodlet not showing/Sims refuse to write for no reason | EA Forums - 12081039 

Does she do it if you give her some time ?

Same Problem. Never had that problem before, now I do. Stopped socializing by blocking doors, let it play out in normal time and tried to block/watch activity queue. Only every 2nd or 3rd books are completed. It really mucks up the writers aspiration.

HI DuffMacDude​ 

would you mind uploading your Sim to the gallery and post the name here ?

I think it's the same as the other issue I linked.

Its the Penny-Nard family, the sims in question is Pipilotta Price.

Have the same issue - even if the sim isn't distracted by anything, it just can stop writing and don't continue. I've tried to write 6 books and i managed to finish only 2: one from the first attempt, another was the only one that my sim decided to continue of all of them. 

Very frustrating

No she doesn't ever complete them no matter how long I leave it. Based on this, I'm not so sure it is the writers block issue?

Same thing happening to me. My sim was able to finish books when he was a child but now that he's a teenager he can start a book, get 90% through the task and then it just disappears. Whenever I try to get him to finish it the task appears in the task chart but disappears as soon as it is first in the queue. I uninstalled script mods and repaired my game and he was able to write one book, then the same thing happened - could start book, get 90% through the book and then unable to finish it. No idea what is happening.

I have exactly the same problem, has been happening for some time.  I had a look at my sims buffs and there's no writer's block (they can start a new book also), they just simply won't finish some books.  

Ran into this twice today. It doesn't happen every time, but when it does, the only thing i can seem to do is scrap the book and start over. It's been making it hard to finish the Ghost Historian aspiration since i have tried and failed to write the necessary final horror book twice now. No writer's block, no creative burnout. Like, I had one fail just now, then went to write another book, (children's so it would take less time) that completed and then went back to try and finish the first one and it failed again, so there is definitely not anything going o that is stopping him from finishing books in general, just THAT one.