Oh, I might be misremembering because I was very small but I could have sworn I used AOL as an ISP and used web browsers (maybe Netscape Navigator?) to browse the web on AOL (maybe version 5 or 6?) in addition to their own weird portal thing which in my very vague memory was a lot like what you are describing.

Is my memory completely false here? It's very possible I'm conflating things from earlier in the 90s with things later in the 90s.

I can't seem to find the book (?) that you're suggesting in a search.