Firefox 48 has "overloaded" the bookmark icon so that in regular view it saves a bookmark, and in reader view, it adds the page to your reading list.

So you first need to open the page in reader view by tapping the book icon in the address bar, and THEN go to the menu and tap the star icon.

Honestly, that is not very self-evident, I'm sure many people will have this same question. Maybe they can merge the star icon with a book or something in the next release.

Source: Save web pages to your Reading List on Firefox for Android

But there IS no book icon anywhere (this is Android I'm using). That's what's missing.

But I found that if I touched the menu button (but not any of the options), THEN touched the address panel the book icon magically appeared and I could then save my reading list item by touching that. Maybe that's what you meant by "open the page in reader view", but even that was not obvious to me!

This is truly an appalling piece of user interface design. Just go back to the old method, please. If it ain't broke don't fix it.

Supplement to the above: that only happened once - I've not been able to add a new reading list item yet! What AM I doing wrong?k

moved to the Firefox for Android queue, from "desktop"

I don't use this feature very much, obviously.

The book icon doesn't appear on every site for me. I see it on blogs, Wikipedia and some random sites. I don't see it on some other pages or on search engines. The layout affects whether the icon appears, but I have not researched the details.

Here's a compilation of screenshots of the address bar on different sites. I get Reader View icons on blogs and on many sites with a "responsive" layout (adapts to screen resolution). I didn't get the icon on a search results page or Amazon.

Thanks so much for your efforts - I do now understand how the revised version of the feature works. I can't say that I welcome it as it seems cumbersome and potentially very confusing though the combination of the favourites and offline lists does have some merit. The use of "responsive" layout sites to enable the feature means that I can't force it on all sites I want to store temporarily. I could save as PDF but it's not so convenient.

All this to remove one button?!

Anyway thanks again for your efforts - I really thought that the feature was broken. I did try to post an answer earlier but somehow I deleted it AND pressed the wrong helpful button too. The shots WERE helpful.