The common newbie bookseller question is: What books sell...?
And of course the answer is everything and nothing... For most B&M (Bricks and Mortar) bookstores...the books that sell are the books that just went out the door...
Essentially, people are looking for entertainment, enhancement, self esteem, or something different when they buy a book... A book is something you do for yourself...or for the person you're buying the book for... But in the end picking a book is a selfish pleasure... Sort of like buying the fancy french mustard instead of the $1 yellow plastic squeeze jar...
I like to buy (drum roll) the OLD, ODD AND OUT OF PRINT...
These are the books that are hard to find... The average Bookscout on Amazon (AZ) isn't going to pick these books.... They usually go for the recent stuff...with 29.95 on the glossy DJ...
I like the out of print stuff...defunct publishers...granular topics... eg. The Third Day at the Battle of the Somme...
Granular topics and highly specialized books...are usually printed in very small editions... And most of these books are eventually remaindered... or just scraped... Who knows how many are available...
Generally, I like to see 20 or fewer available GLOBALLY...
You can find this out by going to Addall.com Addall is a great aggregator site of all the bookselling sites in the world...
They don't list books...they list the listers of books for sale...
A great way to check the price on an odd book....