The minimum page count is generally 48 inside pages. However, the thickness of the paper does have an impact. The true minimum is not a certain number of pages but the overall thickness of the finished piece. Perfect binding requires the book to be a minimum of .125" thick otherwise the pages might not glue properly and could fall out. Therefore if a thicker paper is chosen, 44 or 40 pages might be possible, whereas if a thinner paper is desired, 52 or 56 pages might be needed to get up to the required thickness.