Reddit reviews Batman: The Ultimate Guide to the Dark Knight

Much of what I've been able to find came out in the 2010s so are too late to be it. I found this book from DK that could be similar to what you're describing but I'm not sure it's the right book.

Consult your local librarian, they are likely to have records as to what books they had at the time (even if they've since gotten rid of the book in question) and might be able to tell you the title, author and publisher.

Edit: found another edition of the above, linking it in case the cover rings a bell.