Interesting topic I've never really given much thought until now.
Whenever I get close to finishing a good book while commuting, I usually squeeze a different read in between (or stop reading altogether) in order to save the final ~20 pages until I'm back at home. Especially when the topic at hand most likely calls for a box of tissues at the end - I just can't have public transport get in my way of a hearty sob...
Other than that I rate and mark the finished book as read on Goodreads as well, decide which book to put on the reading shelf next and go on reading.
I'm currently thinking about making myself pause for a few hours upon finishing a book, though, as there's one thing that really bugs me:
Ever since reading so excessively thanks to my eReader(s), I seem to forget books (certain scenes, details, or even endings) more easily / quickly. When on book number 3 or 4, I need to sometimes concentrate really hard to remember how book no. 1 ended, etc.
A friend of mine attributes it to growing old, but I think it's more of a nonstop-reading issue.
I read more now than I used to as an adult and probably as much as I used to when I was a kid and could remember what I'd read for ages. Back then, however, I would not go right on to the next book but would have to find the time to go to the book store or the library first and consequently be without reading material for at least a few hours.
So I'm guessing (might be wrong) that back then the finished books simply had more time to "sink in" as compared to now that I'm turning the last page and opening the next book right away...
No matter how much I love to read, maybe I'm just one of those people who need to pause every now and then in order to be able to fully appreciate a book.
Which brings us back to the rituals:
The final ritual for a book I really (REALLY) liked and will definitely read again more than once or twice during my lifetime would be to buy the paperback version to keep in my bookcase and maybe lend to friends and family who aren't ereading yet.