Greg, I have the following..the original Guatemala-1, the reprint of Guatemala 2, Guatemala philately 1971-1990 thats actually a continuation of Guatemala 2 and The Postage Stamps of Guatemala 1871 to 1999... I reccomend the last one to you...at this point in your collecting it will give you a lot of information and its only about 20 bucks..it gives the total printings of each stamp..some of the higher value airmails there were only 3,000 printed and they are readily available for a few dollars in circuit books and on
eBay !!