The response to my inquiry indicates that the collection was thought redundant.

To which I replied:

John, thank you for your reponse.

I can understand the sense that you were simply providing a set of redudant and duplicate services. I do feel that's less a cardinal sin than it may at first appear.

Though it may be a lost cause, there's simply the durability of URLs, and not breaking links and bookmarks. Adelaide's decision has had widespread impacts well beyond the walls of your institution. Linkrot is a tragedy. Cool URLs don't change:
https://www.w3.org/Provider/Style/URI.html

See also Edward Tufte on the topic:
https://www.edwardtufte.com/bboard/q-and-a-fetch-msg?msg_id=...

There is also the utility of presentation. I'm not generally one to speak highly of Web design and presentation (one of my modest claims to fame is a rather salty-tongued demonstration of what I find to be good style, of which reproducable elements of the title are "Edward Morbius's Website", on CodePen). When I say that Adelaide's eBook site had remarkably good design, I really mean it. It was my first impression on encountering the site, as memorialised at Hacker News: https://news.ycombinator.com/item?id=21391464

I'm very sorry to see that gone. Thankfully the Internet Archive seem to have captured much or all of the eBooks@Adelaide site.

And yes, IA's Wayback Machine is an international treasure. I'd prefer we weren't all increasingly relying on it, however. There's no reason to give even altruistically-minded and future-minded Americans all the prizes. As an archival institution, you may appreciate the value of independent collections, widely separated. That said, I've downloaded several of the works from there for local consumption.

I'm quite familiar with Hathi Trust. Mostly for the reason that, whilst it does contain an impressive collection of works, those are all but entirely inaccessible to me.

Hathi does not allow downloads of materials, even those in the public domain. Full Hathi access is also only available via major research universities. It is not available to the general public over the Internet, or at ordinary public libraries, nor even may college and university libraries below the level of major research institutions.

In Australia that can mean full access requires travel of thousands of kilometers. In somewhat more densely populated developed-world regions (I'm constrasting density, not developedness, with Oz), that can still mean tens or hundreds of kilometers of travel, for what really ought be available as readily as Facebook, TikTok, or Reddit over any WiFi or G4 mobile link.

Hathi have even managed to take such generally exemplary tools as the Internet Archive's BookReader software (truly exceptional) and foul that up -- Hathi's online reader, where it's available, is utterly unusable, and has been for years, on mobile devices. I make heavy use of a 9.7 inch tablet, which is otherwise a serviceable e-book reader. Again: Hathi is by all appearances gratuitously incompatible.

I've lobbied both Hathi and local institutions to change this, with no success. Hathi links are an all but certain pressaging of immense frustration and disappointment.

Gutenberg on the other hand is generally more useful and is among the services I do make heavy use of. In particular, it offers the multiple formats and affordances of online HTML, multiple downloadable formats (generally: text, PDF, and ePub), and has an extensive collection. I really do appreciate that.

I'd at to my (and you might considering to your) list: the Internet Archive, whose books and Open Library collection offer legal access to a wide range of public domain and (for limited borrowing) copyrighted works. I've already mentioned their BookReader software, which is ... mostly usable via tablet (I still prefer downloading and reading locally). Another characteristic is that scans of original books are used, for those cases in which original typography and other print artefacts are of interest.

WikiSource also has full text access to multiple works, and multiple downloadable formats. Another good addition to your recommendations list as these are public domain or publicly-licensed works.

Most useful though have been the online Samizdat press: Sci-Hub, Library Genesis, ZLibrary, and the like. I can appreciate that these likely won't make your suggestion list, and can sympathise, though I feel the sentiments (if not the legality) are ultimately wrongheaded: there is a true real global social benefit in making information freely available with minimal roadblocks or speed-bumps. I often refer to Sci-Hub as the the Library of Alexandra, as in Elbakyan, and feel very much that it holds to the spirit of the original, which you may recall would seize all documents from ships arriving to that harbour city, copy those, and return the copies to the owners, keeping the originals for their own collection. Well into mediaeval times, a principle function of many libraries was offered through the scriptorium, literally the copying room. Somewhat predating Xerox and modern book scanners.

I quite literally owe my ability to perform any amount of meaningful scholarship to these sites, the law be damned.

Several notable modern academics make the case for information as a public good, not only in the economic sense, but in the policy sense. I particularly commend:

Chase F. Robinson, president of the Graduate Center, City University of New York: "At the Graduate Center, we believe knowledge is a public good. This idea inspires our research, teaching, and public events. We invite you to join us for timely discussions, diverse cultural perspectives, and thought-provoking ideas." Introducing a conversation between Paul Krugman and Olivier Blanchard, and a rare case in which the introduction compares favourably with the main act: https://youtube.com/watch?v=zndOEQnMC44

Joseph Stiglitz, "Knowledge as a Global Public Good," in Global Public Goods: International Cooperation in the 21st Century, Inge Kaul, Isabelle Grunberg, Marc A. Stern (eds.), United Nations Development Programme, New York: Oxford University Press, 1999, pp. 308-325.
http://s1.downloadmienphi.net/file/downloadfile6/151/1384343...

I invite you to pass this message along to University of Adelaide library leadership.

Thank you.