This book featured reprints of the first appearances of important characters to the Flash mythos....
....and we'll take a look at these stories below!
KatmosThe first reprinted story is from Flash #105 (February-March, 1959) by John Broome, Carmine Infantino and Joe Giella, with Barry Allen facing off against the "Conqueror From 8 Million B.C."....that being the menace of Katmos (though the cover of the original issue features the Mirror Master, who was in the other story of that book).
After a brief recap of the Flash's origin, Barry faces off against the ancient threat of Katmos, freed by archeologist John Haines (as the metallic monarch used his mind control ray on the man). Katmos then encountered the Flash, even taking control of him for a time, but Barry Allen proved to be too fast for this menace, beating his plans....and still being able to go to dinner with Iris West!
Mr. ElementNext up is the first appearance of another enemy of the Flash, from Showcase #13 (March-April, 1958) by John Broome, Carmine Infantino and Frank Giacoia, that of the "Master Of The Elements", Mr. Element (though this also was not the feature of the issue to make the cover).
Barry faces Mr. Element and his gang (Argon, Krypton, Xenon and Radon, named after the inert elements of the periodic table), with the tricky Mr. Element using pre-prepared tricks with elements to halt the fastest man alive. Mr. Element evades capture, and even calls out the Flash while Barry is on a dinner date with Iris...the villain ruins Barry's night, but the Flash proved he could think fast enough to dash the hopes of his enemy. Mr. Element returns later, in a new identity, that of Dr. Alchemy!
Elongated ManFlash really needed a friend, and he found one in the Flash #112 (April-May, 1960) by John Broome, Carmine Infantino and Joe Giella, at least he would as soon as he solved "The Mystery Of The Elongated Man".
Flash is being out-heroed by newcomer to Central City, the Elongated Man. Elongated Man was really Ralph Dibny, who was fascinated by circus rubber men since he was a kid, found they all drank a soft drink, Gingold, and took an extract from that which allowed him his elastic powers. Flash suspected Elongated Man of recent robberies in his city, and set a trap for the Gingold guardian....but he found EM to have captured the real thieves instead. Flash and Elongated Man tied for the Man of the Year award given by Picture News, and became fast friends after this (with Elongated Man later joining the JLA!).
Star SapphireThe next story of the issue featured the Flash from the Golden Age, Jay Garrick. "The Amazing Star Sapphire" was the one of the menaces of All-Flash #32 (December-January, 1947/1948) by Robert Kanigher, Lee Elias and Moe Worthman (thought Flash foe, the Fiddler, got the cover).
The Flash and Dr. Flura were found comatose, and brought to a laboratory to be revived. While in the lab, the villainous Star Sapphire appeared, with a plan to have her world destroy the Earth (and lured Flash and the lady doctor to it, via a space-time machine). Flash stopped Star Sapphire's evil plan, rescued Dr. Flura as well, returning to Earth. This Star Sapphire later proved to be similar to the Star Sapphire who was the foe of Barry's friend, Green Lantern Hal Jordan (but that connection took a few decades to reveal....).
GroddFlash faced the "Menace Of The Super-Gorilla" in Flash #106 (April-May, 1959) by John Broome, Carmine Infantino and Joe Giella, though this story wasn't featured on the cover...it was the first appearance of Gorilla Grodd and King Solovar of Gorilla City.
Grodd secretly comes to Central City, while Barry's friend, actor Fred Pearson, thinks he's losing his mind (as he performs in an act disguised as a gorilla, but can't remember his last performance, which people say was his best). Really, it was Grodd, hiding for a time, as he searched for Solovar (the king of Gorilla City, who had been captured and was in a circus, hiding his own telepathic abilities). Grodd found Solovar, took the secret of Force of Mind (mind control) from him, and Solovar broke free to find Flash. Solovar explained this to the Flash, who then had to stop Grodd from taking over Gorilla City...which he quickly did (and also promised to keep the existence of telepathic gorillas and their home from the world). Grodd would return many times to face the Flash....
Kid FlashFlash got a little bit of help in his life as he would "Meet Kid Flash" in Flash #110 (December-January, 1959/1960) by John Broome, Carmine Infantino and Joe Giella (in the non-cover featured story of this issue).
Iris' nephew, Wally West, was a big fan of the Flash. Iris asked Barry to escort Wally around town, and hoped to meet the Flash. Barry brought Wally back to his lab, and super-speed around to meet Wally as the Flash. While explaining his origin, a lightning bolt struck, hitting the chemicals and dousing Wally, giving him the same super-speed Barry has. The Flash gives Wally a smaller version of his own suit, allowing the boy to be a super-hero as Kid Flash, as long as he keeps his abilities a secret from everyone. Later, Barry tells the boy his own secret, and Wally even joins with other sidekicks of other heroes to form the Teen Titans.
There were also special features in this issue, like how artist Carmine Infantino drew the Flash, as well as an index of the Barry Allen Flash issues of the time, and a few special Flash firsts covers. While it took a long time for Flash to get another annual, Flash did have a couple of 80 Page Giants (#4 of October 1964 and #9 of April 1965) devoted to his earlier adventures (which you can use the index in the annual to guess which ones they are). Better still, you can get a replica edition of the Flash Annual (which came out in 2001).