You should definitely give some thought to what type of wedding guest book you'll have at your wedding. A guest book is an important keepsake because it serves as a record of all the guests that attended your wedding. It should fit in with the theme of your wedding.
If you're having a traditional wedding, then a traditional type of wedding guest book may work best. Most of these have white covers and plenty of room for the guest's signatures. Even if you decide on a traditional guest book, you could still have a list of instructions beside the book such as "Please write some of your memories of the bride or groom." Otherwise you may get many short comments about how beautiful the wedding is but nothing really personal as many guests aren't sure exactly what they should write.
Photo guest books are popular. You simply provide a camera on the table next to the wedding guest book and leave written instructions asking guests to take their own photos and put the pictures in the book. You could even have pre-written prompts on each page under where each photo would go that ask for name, relation to bride and groom and other information. You can make these prompts totally serious or more humorous — the choice is yours.
Remember that the choice of a traditional or a creative wedding guest book is an important part of your wedding. It's easy to overlook such a small detail when planning a wedding since there are just so many other details to consider. You don't have to have an elaborate book complete with family trees, but you should think about what information about family and friends that you would like to keep in the book. If you plan your wedding guest book well and let your guests know what exactly they are expected to contribute to the book, you and your spouse should have a wonderful keepsake.