You can if the book is wrong Scott -- even if the book is spot on insofar as what a dealer may charge for a coin, if you should go back to that same dealer to sell, you might find yourself being offered 50 percent of book or less. Where you've probably done well is finding rarer varieties here and there which when sold were not identified as such. Irrespective as to whether the coins you may buy turn out to be a good investment or not, enjoy the hobby by learning about the coins you collect and by sharing your ideas and experiences with other collectors, many of whom frequent this forum.