Mark books read/unread/in-progress.
Show top 10 / bottom 10. Show only in-progress or unread.
Rank only in-progress or unread.
Track books by title, author, and series. Default is to recognize "by" or "(series)" and automatically sort into relevant fields.
- But also almost nothing is actually needed.
Store progress as a numerical value? (Unread = 0, read = 1, in-progress in-between? Too easy to forget how it works?)
Store pages as an option,
- allow a weighted priority based on remaining percentage or whatever.
Store items as an array instead of object, because that makes the JSON output more consistent -> smaller JSON commit differences.

I think the opening UI should be to display the top 10 books in-progress (sort order customizable by user), where pressing a number key allows the user to immediately enter an updated progress. Additional alphabetic keys are an option to access other features. This way tracker use is near frictionless. (0 maps to 10)

data structure of an item

{
  title = "Title",
  author = "Author",
  series = "Series",
  pages = 100,
  priority = 0,
  progress = 0.5,
}

title, author, series, and pages are optional.
At least one of title, author, or series must be defined.
priority is the ELO ranking, initializing to 0.
progress represents read/unread/in-progress status. 0 is unread, 1 is read, and anything in-between in a percentage of progress.

the name

A combination of asymptote - because you will die before you finish your reading list, always getting closer but never arriving - and tome.