I'm retired. My last job before retirement was paid by an NIH grant to develop online classes teaching elementary computer programming for Tribal Colleges.
I used Moodle and lots of software I wrote myself. I also used the proprietary "Desire to Learn" and I did prefer Moodle. The biggest drawback for both systems (Moodle and Desire to Learn) involved interactively creating supplementary reading material.
Yes it is possible to use Moodle to make online ebook-like reading materials but I found the output less satisfactory than real Epub3 content produced by the Open Source Sigil software.
Epub3 created by Sigil is expected to be downloaded to a phone tablet or desktop computer and then displayed with software installed on the device. There was and still is no way to put Epub3 content on a webserver so it can be displayed by a browser, so the epub3 content can be embedded inside a surrounding system.
So I wrote that software. I can upload any valid epub3 file to a web server and unzip it there, on the server, and then display it in ebook like format, complete with Table of Contents and dynamically displayed page-by-page output.
I have a hunch this software would be a useful addition to Moodle. I'd be willing to work on an epub3 plugin mechanism to Moodle--if others thought it would be useful.
Note that epub3 is capable of displaying text, still images and embedded video, all packaged in a book-like format, complete with a Table of Contents. And to produce that output the author (teacher) does not need to be able to write program codes. They do have to learn how to use Sigil.
Would Epub3 ebooks embedded inside Moodle (so the ebook would still be surrounded by the global Moodle navigation links for that course) be a useful addition to the Moodle system?