I buy and sell books and dvds on flea bay now and again £60 this week but bought a 30p book afew weeks back thats worth between £300 to 1k ,the best thing to do is to look at trends or upcoming movies or books that could be made into movies ect ,some dont always work ,some do i.e i have some good vibes about jonothan strange and mr norrell so ive bought a first edition first print signed ,thers also sk,s the dark tower coming out as a trilogy and tv show , i also take photos of books stacked in charity shops , go home and research then go back if i get a bite