These books were always checked out, and if one was actually on the shelf -- didn't matter if you'd read it before -- you checked it out and read it again. The one I had memorized was The Incredible Hulk, and it was the first one that I purchased for myself as an adult (from a backwoods antique shop) that set me on the path to nabbing them all. Some of the books are assembled by theme (Origins of Marvel Comics, Bring on the Bad Guys, The Superhero Women) while the ones that centered on specific characters contained their origin issue and usually three or four stories that captured the essence of the characters, as curated by Stan Lee.
I'm assuming Lee curated them, as he gets sole cover credit as the writer on all of the Fireside books, whether he wrote all of the interior tales of not. There's no credited editor on the books, but the small bits of prose and historical context that separates the issues within the Fireside books certainly sounds like Stan Lee (and he does credit the respective creators within the interior pages). Because of the time in which they came out (late 70's, while the Marvel Superheroes were just over a decade old) and because Lee supposedly picked the stories, the Firesides provide a timely snapshot of what Lee felt defined these characters (most of which he had a hand in creating). You end up getting these superheroes in their purest forms, and the Fireside books remain one of the best ways to quickly learn about Marvel characters.
Most of the Firesides can be found for peanuts on Amazon and eBay, with the exception of Fireside's Silver Surfer -- the only book that tells a full-length original story and ended up being the final collaboration between Lee and Marvel cornerstone Jack Kirby. If you have kids in your life, interested in Marvel from the blockbuster films, the Firesides still can't be beat.
According to Wikipedia, the Fireside collections are as follows:
Links to purchase through Amazon are provided above, and the books are pretty much all available in both paperback and hardback versions. Wiki doesn't list Mighty Marvel Team-Up Thrillers, a 1983 collection that looks just like a Fireside book (including the "By Stan Lee" cover credit), but without it here in front of me, I can't confirm that it's actually from this publisher.