Pretty rare to find this. Now's your chance to pick up a copy of that Marathon book by D. Alexander Smith. Here's the blurb from the seller:
"In deep space, the enemy need not always have tentacles and breathe methan. The most deadly enemies will be far more familiar ... This mass-market sized paperback book is in Very Good condition. This book, written by D. Alexander Smith, was published by Ace Science-Fiction in 1982. As seen in the photo below, there is a moderate sheen of general wear to the cover and spine of this item, but the cover retains a good measure of its original eye-appeal. The interior pages are clean and highly readable as well. Check out our other auctions for more comics, magazines, toys and rare items!"
Opening bid is $3.99. A bargain compared to how much you'd have to pay some companies to locate this out-of-print book for you.
Cheers
Hamish