What's the value of these book?

[Ahmad Alshaikh Ali]

I want to sell copies of some book which are all out of print as far as I know, so I was wondering if someone can tell how valuable are they:
-Williamson's Wonders
-Essential Dai Vernon
-By Forces Unseen
-Complete Works Of Derek Dingle

I tried looking for them on ebay to see the prices but I couldn't find any of them except derek dingle's book.

 

[VagueTheory]

I wish to point out that the Complete Works of Derek Dingle is not out of print because Richard Kaufman still sells copies on the Genii website.

As for the other ones, the value is only as much as the buyer is willing to pay. I don't believe each book has a specific worth. If you really want to check, put them up for sale on The Magic Cafe or other magic forums and see what people are willing to pay for them.

I did not know that By Forces Unseen went out of print. That was a surprise to me.