The concept of this collection is that it contains stories that were developed many years ago, but not published at the time for various reasons. For example, the first story features Dr. Strange in an adventure that was plotted and drawn, but not yet scripted when the comic it was intended for was canceled due to low sales. It's a cute yarn that describes how the early Dr. Strange acquires his Greenwich Village brownstone house. Next comes a Thunderbolts story that was written as an inventory issue for use in case deadline problems created a hole in the schedule; it sat for so long that its main character, Jack "Nomad" Monroe, was killed off in the regular continuity and so it was too outdated to use until Marvel decided to find and print these "lost" stories.
Next is another inventory issue, never printed, for Marvel Team-Up whose breakdowns were drawn by the legendary Steve Ditko, a very nice treat for fans of the reclusive comics genius. Next we have a Defenders inventory issue that was plotted and drawn but not scripted since it wasn't needed to fill a scheduling gap. In this case, no one could figure out what the original writer intended so a new script to fit the artwork was crafted. Kurt Busiek came up with the new story and Mark Bagley did the very attractive art.
Finally, there's a Gambit story drawn by George Tuska with guest stars The Champions, another unfinished story where the script was lost or never written and a new script was written by Scott Lobdell to fit the pictures.
This makes for a very odd book, but vendors at the time of this review were offering it for less than $3 (it was originally published for $15) and it's a huge bargain at such a discount. And it is a true anthology, featuring a wide variety of characters instead of a story arc featuring a single character or team.
I hope I've given you enough information to decide if it's your cup of tea.