The Old West is one of the most popular series by Time-Life. Each book is bound in brown leather and features a nice picture on the cover. I have never personally read one of these, so I can't vouch for the content.
One thing to note for collectors, though; there have been several different editions of this series. Most volumes have been printed at least twice, and several have been printed three times (and each iteration has it's own ISBN number). Though the different editions seem similar, the volumes published in 1990-1991 and since have different covers, so if you are looking for a matched set, make sure all of your books are from the same edition. Also, make sure the set listed includes the Master Index! The Master Index for this series sells for around $20-$30 by itself; about 4 times as much as any other individual volume.