id look around on the internet to try and see what kind of value you have, if you dont know already.
if you know what youre looking to get for them, id probably start with putting them on ebay to see what kind of offers, if any, you can get for them. I wouldnt put them up for a straight auction at first, I'd take whatever youre looking to get for them and add a bit too it and make that the Buy It Now price and include the best offer option. that way if someone is interested they can send an offer and you can either accept, or counter.
here is one of the books....I see it on eBay twice. once sold, and another one that is currently up for auction.
http://www.ebay.com/itm/1939-first-...t=Antiquarian_Collectible&hash=item4d106d246b
http://www.ebay.com/itm/On-The-Trai...t=Antiquarian_Collectible&hash=item2a322099d7
the sold one doesnt look to be in great condition. I am no expert on books though just judging between the two. the current auction looks to be in much better condition. I am not sure how accurate their asking price is but they have had no offers on the books so maybe it is slightly off. they are likely doing the same thing in listing it for more than they would actually accept.
something to remember, just because they are old doesnt mean they are rare.
http://www.ebay.com/itm/LIVE-COALS-...t=Antiquarian_Collectible&hash=item20d8187a03
that is a book by the same author as one of yours and it only sold for 40 bucks. yours could be really rare, but just an example of really old stuff not being worth a fortune.
id definitely poke around and find out what the values are before i went to sell them. you dont want to take them to some auction house that charges a 50% commission and only get a few hundred bucks for them.
there must be places online that can give you an idea for a value. maybe even an antique book message board or something if you signed up and showed them what you had someone could shed some light.
