THINK TWICE ABOUT STARTING AT 99¢
A long time ago, sellers could start items at 99¢ and generate a bidding war. Over the years, eBay has changed. Yes, starting at 99¢ may work great for in demand items, like a popular electronics gadget. But for vintage and one of a kind items, or media of almost any type, I have found that items started at 99¢ usually end at exactly that -- 99¢. Your time is more valuable than that -- and shipping supplies may end up costing you almost as much as you make! I never recommend starting that low.
THE IMPORTANCE OF RESEARCH
The easiest way to see what your item is worth is to do a search on eBay. After you search, you will want to sort by price, and then look at the difference in Auctions Only items (tab at top of screen) and Buy It Now Only items (tab at top of screen). You may also want to look at the left-hand side of the screen and click on Completed Listings.
With books, you are likely to see a very broad spectrum of prices. I always disregard the "penny seller" listings (big companies that list many, many books for under $1). I try to look for listings by other "regular sellers" to get an idea of pricing. If a book is in good to very good condition, or if it fairly uncommon, I usually price near the upper end of the price range -- but not the highest price.
I also recommend Best Offer for items, but that is a future blog post here!
CHECK OTHER SITES
If your item is rare, you may want to do a Google search for it as well. I check more uncommon book titles on ABEBOOKS (http://www.abebooks.com/) for prices, and I also like the used book search at Addall (http://used.addall.com/). There are other item-specific sites for different categories.
WHEN IN DOUBT, HAVE A DEFAULT PRICE.
When in doubt, especially with items I cannot find online, I start auctions at $9.99. This has worked well for me in the past. I highly recommend having your own default price, especially for auctions. My fixed price default runs a bit higher, as I also include Best Offer.
I hope these pricing tips are helpful, and I hope you make great sales on eBay!