Alex Raymond created Flash Gordon as a full page comic strip on January 7, 1934. The strip continues today, though only in reprint form, alas. There have been reprints from Kitchen Sink (these are the best), Dark Horse, Comics Revue, and many other publishers. Some of these are still in print, others can be found on ebay. This book, from Checker, reprises the Kitchen Sink material.
The strip had its ups and downs, but most collectors agree that it was in its prime in three eras, the Alex Raymond era from 1934 to 1944, the beginning of a revived daily strip, by Dan Barry, Frank Frazetta, Jack Davis, Wally Wood, Harvey Kurtzman, and just about the whole E.C. Comics gang, from 1951 to 1955, and the Harry Harrison era, from roughly 1958 to 1964. (Harry Harrison also contributed to E.C. Comics, and wrote The Stainless Steel Rat.)
It is good to see these strips back in print.