I suggest reading online and then saving chapters and sections as permanent PDFs. But almost all of these ebooks can be downloaded, almost all the time. See these slides with screenshots. Also, the U of New Mexico guide is helpful. And there are links to more EBSCO/ProQuest help pages at bottom here.
However, the main problem I've seen is getting the book, once it's downloaded, actually into the reader. Safari works flawlessly for me. Try that if you have an iPad/iPhone. Chrome, Firefox, and others often do not work. I'd like to hear about problems and successes.
Zoom help, if you need it.
--John Wiswell, August 2020
Subject encyclopedias are a good way to start research on a new topic. Articles in subject encyclopedias are usually written by experts in their field.