That's very kind of you. The whole book is actually a bit of a mystery. The binding is very old, but from the look of the book block itself, it's not the original one. Before it was rebound, the title page was repaired, the frontispiece was already missing, and both title page and the back of the final page are so dirty that it must have been lying around without any boards for a long time to reach that state. It also had coloured endpapers which I've never seen in a book published as early as 1815. Anne had written her name and address in pencil on the endpapers as well as signing just her name on the title page and final page in ink, so she must have owned it after it was rebound. She'd added a date after her name on the title page, but unfortunately it comes at the very end of the page, the corner of which is missing, and the vital last two numbers are no longer there.
The long "s" has been throwing me. I know it was no longer used in printing after the very early 1800s (1805 is the latest book I have in which it features), but it did remain in handwriting for longer. I thought it had pretty much died out by the mid 1800s, certainly amongst the younger generation, but when I put everything together it's starting to make sense that Anne may well have been the person who had the book rebound, but she wasn't the first owner of it as I'd assumed.
It's really only due to your research that I'm beginning to be able to piece the book's history together and I very much appreciate that, but if I'd realised all of this before, I wouldn't have started the thread as it makes it far less straightforward than I'd originally thought and without a firm date of any kind, it's probably going to be impossible to find a definite answer.
It's possible if Anne and William married in 1812, that Thomas wasn't actually their firstborn. Could there be a daughter Anne who was already married by 1841 to whom her mother passed on the book?