For your consideration, here is a Lot of 2 Martian Series Paperback Books by Edgar Rice Burroughs, no. 9 and 10, published by Ballantine Books. Both of the books are first printings. Both have some wear and creases by the spines. They have some tanning of the pages from aging. Items pictured are the actual items up for sale and come from a non-smoking household. (165.254y-.13sc)

Here are the books with the number in the series, title, publishing date, number of pages and additional condition notes:

9. Synthetic Men of Mars, June, 1963, 160

10. Llana of Gathol, August, 1963, 191, missing a bit of the covers in the corner for the front and back covers, has check marks by books listed on the last page, has writing on the top end pages