The Standard Guide to Golden Age Comics is a nice book to have when I'm looking online for books, but the prices don't seem much different than what Overstreet has.
If you're only "determining their worth" out of curiousity, use Overstreet or the Standard Guide, get familiar with grading comics & how to price them, and have at it. You can also go to Mile High Comics' website which has a large selection of books with their different values listed. I would suggest if you were going to use eBay to determine the price of your books to look through Store Listings only (sort by lowest price). Completed Auctions will only tell you what people were willing to pay for the books while fighting with someone else for it, not what they may actually be worth to a serious collector.
If you (or anyone else, really) are going to list the comics on eBay, make sure you put them in the right Category AND Sub-Category. While that might seem like an odd thing to say, I've picked-up quite a few items dirt-cheap simply because the person listing the item put (for example) an action figure in the "Books & Magazines" category. If you're planning to have someone else list the books for you, make sure they know what they're doing. Just because someone makes a living selling on eBay by listing other people's stuff, doesn't automatically mean they're good at what they do. Again, I've purchased things off eBay at a fraction of the price I should have paid simply because it was mishandledby a third-party seller. And Last But Not Least, selling on eBay means taking the chance that you won't get full value for the book. HOWEVER, Golden Age books, even in Poor Condition, Coverless or Incomplete, can generate some solid interest if they're rare.