The story told by the author is his/her signature. having them write inside "HI Chimps" with a sharpie is dumb. They don't know or care about you. All they care about is pushing the book because their publisher that paid them to write forced them.
Sometimes. The signature can add, sometimes significantly, to a book's value. Get a book signed by Nora Roberts, not so much. Get 1st ed. signed by Cormac McCarthy and you've probably got a $1,000 book. Someone like Thomas Pynchon , $100,000. JD Salinger's valuation would be up to Sotheby's.
/and i just get a simple signature.