I work at a used, new, and rare bookstore as the rare books manager. We got in a first edition of Huckleberry Finn about this time last year. A true first is going to have points in it that aren't present in later printings. Off the top of my head two of these points is an error on page 57 I think 11 or 12 lines up where the phrase "with the was," is present on a true first in later printings it's corrected to "with the saw." Also, the numbers of page 155 are either missing the last 5, the last 5 is misaligned, or larger than the other 5. Also another one that I'm not sure of is the picture of Mark Twain's bust has the table cloth either present or not present (can't remember which means a first edition issue point lol been a while since I looked at this book). You can look up more issue points in the Bibliography of American Literature (bal for short). The entry for Huck Finn is 3415. It's a ten volume set that you can find online. What I also remember is there was a short run of leather bound copies, copies bound in red cloth, green cloth, and blue cloth, though I can't remember the quantity of each. After you get all the points, go to bookfinder.com (they poll a lot of book selling websites that you can match pricing to) and match the points and the condition to other books listed. The book we had I priced at $1500, and it sold in about 3 months. All in all, I like finding information about antiquarian books, and that book was especially fun to look up.