If you want to maximize your sales price, do not sell them as one lot.  Look at what they are selling for individually on eBay if prices are available, then offer them to buyers at that price, adjusted up or down for condition, on the acaeum and dragonsfoot web-sites.  You can also get helpful quotes on the value of items on this forum when you post pictures.  Without pictures, it's significantly harder to give accurate quotes.  And if you supplement the pictures with information about any smells, rust, tears, highlighting or writing within the books, the estimates get even better.

Make sure you have quality pictures and descriptions of each item.  The items which don't sell after a couple of weeks should go up on eBay again with good pictures and descriptions.  Finally, there are people who send you offers by private message.  If there is any doubt about the worthiness of an offer, feel free to ask this forum if an offer is worthwhile.