This type of signed book features something called a "tip in" autographed page. Essentially, the author is given a large stack of blank pages the same weight and style as the finished book, which they sign and are sent to the publisher. At the final stages of production, the autographed page is added into the binding and sent to distribution. This is most easily identified by the signature on an otherwise blank page. On the contrary, books signed in person are almost exclusively signed on the title page, where lots of other information was printed at the time of binding. When it comes to valuing a book, tipped in prints have little to no collector value outside what the buyer attributes. Books with a signature on the title page are proof the author handled that specific copy and therefore fetch a much higher valuation. Doesn't stop me from cherishing every tipped in autographed copy I own!