The book opens with a brief overview of what Mindjammer is all about and an excellent concise summary of how the Fate ruleset works. Even if you do not intend to play Mindjammer, this is almost worth picking up for the Fate overview alone - excellent for introducing new players to the game mechanics. However for those who will be playing Mindjammer, comments relating to the game are woven through it, so again even if you don't need the introductory adventure, your players might find it a useful quick reference to the rules.
Next, four pre-generated characters are provided to enable you to jump right in and play - the rules summary doesn't explain how characters are created, it concentrates on how to actually play the game. They are carefully interwoven to create a coherent group with reasons to be together at this time and place, a nice example of how to create a party for this game... although they may or may not want to form a longterm relationship, as two of them are fugitives who have been captured by one of the others! One is a sentient ship, complete with a synthetic human analogue avatar for those occasions when being a starship in inconvenient.
Finally, there's the introductory adventure, which takes the party to Yand, a rediscovered world on the edge of the New Commonality of Humankind's sphere of influence. It is hotly contested by both the Commonality and a neighbouring (and hostile) bunch called the Venu. There's a lot of background about the planet itself and its current situation crammed in here. It's a fascinating and well-developed system. The adventure itself revolves around retrieving a kidnapped agent of the Commonality, and spreads over eight scenes - although you don't need to play all of them. For example if you only have a short playing time, like a convention slot or a single evening, you could get by with three scenes. There's a detailed timeline to help you stay on track. The adventure is exciting, and also demonstrates how the Commonality operates which - as it is all-pervading - is a good guide as to whether you and your players are going to enjoy playing Mindscape. There's a lot going on, a lot to keep track of, and the GM should study the adventure thoroughly before play begins to be able to stay on top of it. If the party is successful, other published adventures make for good follow-ons, assuming the party stays together, giving you the beginnings of a campaign as agents of the Commonality.
This is an excellent introduction to this game which makes the most of its particular character and should give your group a good idea if this is a system they'd like to play longterm.