[NTLK] Converting NewtonBooks to ePub

[Victor Rehorst]

A complete shot in the dark here, but could it be - or are you referring 
to - Newton Streamed Object Format (NSOF)?

Eckhart Köppen's RDCL builds a command-line tool `nsof` that can decode 
NSOF to XML or YAML.  There are other, earlier implementations of NSOF 
as well.

On 2026-02-24 19:51, J Caffiney wrote:
> I've been looking at the NewtonBook binary format lately, trying to figure
> out if there's a reasonable way to extract book content from .pkg files and
> turn it into something readable on today's devices.
>
> I've managed to get some basic conversions working — NewtonBook .pkg to
> ePub. Results are rough but readable. So far I've run it against a few
> titles from UNNA: The Art of Newton, InvesTerms, and the NS BASIC Tech
> Notes. Chapter structure and text come through. Styles are hit or miss. I'm
> happy to share the converted ePubs if anyone wants to see how they turned
> out.
>
> The interesting challenge is Newton's internal format — UTF-16 big endian
> text, the ref encoding for objects, and the way book content is nested
> inside NOS frames. Apple documented some of this in the Formats spec but
> there are gaps, especially around how style runs map to the actual text
> boundaries. Robert Sundling's PKGDUMP (
> https://github.com/RobertSundling/Newton-PKGDUMP) was helpful for
> sanity-checking the package structure, but the book-specific content layer
> is mostly undocumented territory.
>
> Does anyone have deeper knowledge of the format — especially the
> relationship between style runs and text content in book parts? I've been
> filling in the gaps by trial and error, but I'd rather not reinvent
> the wheel.