Sign in books have been around forever at weddings. I remember the tipical white book you pick up online or at Micheals. the book has lined pages and comes with a big white feathered pen in a holder. It kinda looks like a pen from signing the Declarations of Independance. The book is a must have to allow your guest to sign in and leave some thoughts.
Digital photography and the new photo books are a new twist on the old book. Your photographer can design a custom photo book from your engagement photo and add some of your own photos including any baby and family photos.
You can see samples at, http://www.facebook.com/media/set/?set=a.142203649165796.38624.140651652654329
or check out the video of real book at a wedding, http://www.facebook.com/video/video.php?v=473524959039&oid=140651652654329&comments