In general, autograph books should be assessed on an individual autograph basis, as that is how the highest value is attained. That is because an autograph dealer will cut out the best autographs and sell them each one by one. The overall value would depend on how many autographs and exactly who, though on average, you can estimate about $25 - $45 per signature in the book. You can contact Profiles in History, an auction house specializing in movie memorabilia to get a free auction estimate through their website.
Here is the link to their site for you: www.profilesinhistory.com/
I am just checking in to see if you have any additional questions about your item?